refactor(lang): remove the defer state-body extension

[devin-ai-integration]

What and why

defer <event> [, <event>]*; inside a state body was an OpenSysML-only extension — SysML v2 has no deferral notation — and PR #669 already made the SysML v1 migrator write every deferred signal in standard notation (ordered buffer item, do-action accept loop, exit-action flush, @MigrationMetadata::DeferredEvent provenance). This PR removes the extension itself from the language, the runtime and every surface:

• Lexer / parser / AST. defer is no longer a contextual keyword; ast.DeferMember, StateNode.Defer, the codec/dump/succession handling and parseDeferMember are gone. defer is an ordinary name (attribute defer : Real;, action defer, state defer, defer.x — golden tests/parser/testdata/parse/defer_ordinary_name). A legacy defer <event>; member is one parser diagnostic, code defer-notation-removed, spanned on the word, with an ErrorNode in the tree; recovery consumes to the semicolon or the next member start, so defer Ping state b; still yields substate b.
• Semantics / checker / IR / views. No defer scopes, resolution, multiplicity or trigger typing; nonstandard_notation.go no longer knows the word (it is a parse error in both modes, not a warning escalated under -strict); StateGraph.Deferred, the inheritance merge and the Sig / defer view labels are removed.
• Runtime. deferred, defersEvent, deferringStates, deferralOutranks, recallDeferredEvents, DeferredEvents(), Decision.Deferred, Dispatch.Deferred, the deferral branches of dispatch, the state-deferral footprint in check_reduce.go and the snapshot/debug serialization of held events are gone. A standard-encoded deferral runs on the ordinary do-behavior and send machinery, unchanged. A signal queued from outside the model by name (QueuedEvent.Signal) is what that name denotes to the exhibiting part, as a send written there is, and is taken by conformance; a name the part sees no signal definition by is resolved in the scope of each accept it is compared against (Message.TypedByAccept, messageSignal) — matched by conformance where that scope declares it, by name where none does — and typed by the accept that takes it, so a machine-local private import matches supertype accepts and binds its payload without the injection choosing between scopes.
• Frontend / client. Acceptance.Deferred is removed from the Go client and gRPC conversion (Acceptance.Resumes stays); the REPL's %current "Deferred by the active state" report, the %send wording and the defer completion entry are gone; LSP publishes the removed-notation diagnostic in both modes.
• RDF. sysx:DeferMember / sysx:deferredEvent are removed from the ontology, the writer and the reader; a legacy Turtle graph carrying them is refused with a diagnostic naming the standard encoding rather than read with the member dropped (tests/export/behavior_test.go).
• Shared standard encoding. internal/translate/deferred is the one writer of the buffer / accept-loop / exit-flush encoding; internal/translate/migrate/states.go and the PSSM referee (tools/referee/pssm/emit.go) both render through it (unit-tested in deferred_test.go; the migrator's TestStrictDeferredSignals* / TestDeferral* and the PSSM suite test exercise it end to end). The migrator's output is byte-identical to develop.
• Fixtures. The extension-only conformance cases (state_deferred_event, state_deferral_outranks_*, state_deferral_nested_override) are retired and each scenario the standard notation can express is re-pinned in standard notation: state_deferred_signal_kept_and_replayed, state_guard_reads_deferred_payload, state_nested_parallel_region_owner_behavior, state_then_skips_non_feature_members, plus four state_deferred_buffer_yields_to_* cases that pin the standard behaviour where the extension's priority rule used to hold the signal back (a transition that is enabled fires). state_deferred_test.go is removed; its two tests that did not depend on the extension (TestUndeferredEventIsDroppedWhereNoTransitionHandlesIt, TestExitedNestedRegionDoesNotReactToTheSameEvent) live on in state_composite_transition_test.go.
• PSSM referee. Writes the standard encoding; Deferred 007 (a deferred operation call) is not-expressible; the Deferred 006 rows (a deferral in a state an unguarded completion transition leaves) are not-expressible; see the bucket table below.
• Parser diagnostic codes (merged from develop, PR fix(grpc): report the parser's warnings as the workspace does #751). parser.AsDiagnostics is the one mapping every frontend uses; its errors are coded by Diagnostic.ErrorCode() — the diagnostic's own code when the parser gave it one (defer-notation-removed), else syntax — so the removed-notation code survives the refactor on the LSP, gRPC, REPL and edit surfaces.
• StateMachines metadata library (merged from develop, PR feat(state-machines): express pseudostates and deferred events as standard metadata #639). The pseudostate annotations stay — #choice state, #junction state, #shallowHistory state, #deepHistory state, their nonstandard-notation quick-fixes and the migrator's use of them. Its second half, event deferral as metadata (deferredEvents, metadata def <deferred> DeferredMetadata, #deferred ref : Ping;, lowering into StateGraph.Deferred, the defer e; → #deferred ref : e; quick-fix, eight *_metadata conformance fixtures, the %current and gRPC reporting of held events), is removed here rather than kept beside the standard encoding: StateMachines.sysml and the stdlib snapshot, internal/ir/lower/state_metadata.go, nonstandard_notation.go, the LSP code-action test, the workspace and PSSM validation tests, docs/project/statemachines-library.md, the guide/reference pages and the state-machine-metadata.* changelog fragments now describe pseudostates only, and a legacy defer member is a parse error in both modes, not a deprecation warning.
• Rejection oracle. x05-defer-member.sysml is now rejected by OpenSysML in both default and strict modes (verdicts.go + docs/project/pilot-rejection.md): 311 cases, 302 both reject, 0 only the pilot, 9 only we, 0 both accept (2 of them agreeing only under -strict; -conformance default gives 300 both reject, 2 only the pilot). The baseline is re-recorded on the merged tree for one movement that is develop's own: PR feat(state-machines): express pseudostates and deferred events as standard metadata #639 made require outside a requirement body (x08) a parse error, so it moved from strict-only to both-reject by default — a build of origin/develop rejects it the same way — and develop's baseline had not been re-recorded; pilot-rejection.md adjudicates it. The undeclared-signal lint merged from develop covered a defer <name> member as well as a when <name> trigger; with the member gone it covers when only (passes/lint_undeclared_signal.go, its tests and the lint's documentation).
• Docs / editors / examples. Guide, reference, spec-compliance.md, pssm-migration.md, pssm-referee.md, pilot-rejection.md, the design notes (pseudostates.md, precise-semantics-alignment.md, orthogonal-regions.md, scheduling.md, …), the VS Code grammars (regenerated) and snippets, examples/self-model and the README lose the extension. One "removed" note stays in docs/reference/grammar/README.md and points at the standard encoding (docs/reference/sysml-v1-migration.md, Deferred signals).

Semantics that are no longer expressible (accepted losses, documented rather than recreated)

Lost	Why	Documented in
The extension's priority rule — a deferring (sub)state outranked a transition out of an enclosing state or in a sibling region that accepts the same signal	The standard encoding is a parked accept in a do behavior; an enabled transition anywhere in the configuration fires first	docs/project/spec-compliance.md (deferred-signal rows), docs/reference/grammar/README.md, docs/internals/design/precise-semantics-alignment.md § deferred events, the four state_deferred_buffer_yields_to_* conformance cases
Replay order across different signals	Each buffer flushes in its own for loop; UML leaves event-pool order open	docs/reference/sysml-v1-migration.md § Deferred signals, docs/project/pssm-referee.md (Deferred 001 / 005)
Deferred operation calls	Standard buffering keeps signal occurrences only	docs/project/pssm-referee.md (Deferred 007), docs/project/pssm-migration.md, docs/reference/grammar/README.md

Specification basis

The SysML v2 textual notation has no deferral production in a state body; event deferral is a UML state-machine / PSSM notion, which SysML v2 models with an ordinary buffer, accept loop and flush. The compliance rows for deferred events in docs/project/spec-compliance.md move from the extension to the standard encoding (✅ for the kept-and-replayed signal and the guard reading its payload; the priority rule and the pooled replay order are recorded as known losses).

How it was verified

Gates (all on the branch head; gofmt -l . prints nothing):

go build ./... && go vet ./... && gofmt -l .                       ok
go test -count=1 ./...                                             ok for every package except internal/frontend/lsp (see below)
go test -count=1 -C tools ./...                                    ok
go test -race ./internal/exec/runtime/... ./internal/syntax/...    ok
go test -run TestStdlibConformance ./internal/workspace/libs       ok
go test -run 'TestGolden|TestNegative' ./tests/parser ./internal/syntax/parser   ok
go test -run 'TestExecutionConformance|TestExecutionTrace|TestRuntimeRobustness' ./internal/exec/runtime   ok
OPENSYSML_REQUIRE_TRAINING_CORPUS=1 go test -count=1 ./tests/corpus -run TestTrainingExamples   ok
OPENSYSML_REQUIRE_PILOT_CORPORA=1   go test -count=1 ./tests/corpus -run TestPilotCorpora       ok
OPENSYSML_REQUIRE_PSSM_SUITE=1      go test -count=1 ./tests/corpus -run TestPSSMSuiteMigration ok
OPENSYSML_REQUIRE_TRAINING_CORPUS=1 OPENSYSML_REQUIRE_PILOT_CORPORA=1 go test -count=1 ./tests/corpus -run TestCorpusRoundTrip
    corpus round trip: 358 files: 358 stable, 0 whitespace-only, 0 graph-diff, 0 unwritable, 0 unparseable, 0 refused  (no movement)
go run -C tools ./cmd/pssm-referee -check                           pass 52 / fail 12 / not-expressible 34 / differs-by-design 5 (reproduces the baseline)
go run -C tools ./cmd/pssm-referee -json -jobs 1  vs  -jobs 8       byte-identical reports
go run -C tools ./cmd/pilot-reject -check                           311 case(s): 302 both reject, 0 only the pilot rejects, 9 only we reject, 0 both accept
go run -C tools ./cmd/pilot-diff -check                             380 files, 345 fully agreeing, 38 agreed, 40 ours, 1616 pilot's — develop's figures; only the examples digest re-recorded on the merged tree
make docs-counts                                                    documentation counts current
python3 scripts/changelog.py check && python3 scripts/check-doc-ids.py   ok
rg -n '\bdefer\b' --type-not go -g '!**/testdata/**' .             only Go `defer` statements in embedded Go snippets, the "removed" notes, historical CHANGELOG.md entries and the rejection-oracle x05 description remain

internal/frontend/lsp: the TestWire* / TestRunServes* stream tests time out (30 s waiting for publishDiagnostics) on this machine on origin/develop (074aceb) as well as on this branch, identically; every other LSP test in the package passes, including the new TestPublishDiagnosticsReportsRemovedDeferNotation. Treating it as an environment issue here — CI will tell.

Pilot differential baseline (docs/project/pilot-differential-baseline.json): develop re-recorded it (345 fully agreeing / 40 only ours / 1616 only the pilot's) with its own adjudication in docs/project/pilot-differential.md, and every diagnostic figure reproduces on this merged tree with pilot-diff -check, so this PR carries develop's figures and prose unchanged. The one thing re-recorded here is the examples root digest, because the corpus under examples/ loses the extension. The branch's earlier Parameter effective-multiplicity round section is withdrawn: the end-feature multiplicity warning it recorded on examples/parser_features_demo_connectors.sysml:108 no longer fires once develop's nested action-body source-multiplicity fix is merged in, and the advisory movement is develop's own. make docs-counts passes.

PSSM referee bucket movements (docs/project/pssm-referee-baseline.json, pass 60 → 52, not-expressible 30 → 34, differs-by-design 1 → 5, fail 12 unchanged):

Test	Was	Now	Reason
Deferred 001	pass	differs-by-design	the flush re-sends kept occurrences behind what is already queued; PSSM replays the deferred pool ahead of later arrivals
Deferred 003	pass	differs-by-design	a transition out of the enclosing state fires on the signal; the extension's priority rule held it
Deferred 004 A	pass	differs-by-design	a sibling region's transition fires on the signal the other region keeps
Deferred 004 B	pass	differs-by-design	same, nested deferring substate
Deferred 005	pass	differs-by-design	replay order across different signals is not preserved by per-signal buffers
Deferred 006 A	pass	not-expressible	a deferral in a state an unguarded completion transition leaves: the completion fires before the accept loop can keep anything
Deferred 006 B	differs-by-design	not-expressible	same
Deferred 006 C	pass	not-expressible	same
Deferred 007	pass	not-expressible	a deferred operation call; the standard encoding buffers signals only

TMT end-to-end (TMT-2024x.mdzip + TMT_mtip.xml, this branch vs a build of origin/develop at 074aceb, default and -strict):

• rg -c '^\s*defer ' out-*/TMT.sysml → 0 in both modes, both builds.
• DeferredEvent occurrences → 823 in both modes, both builds.
• TMT.sysml, TMT.migration-report.txt and TMT.migration-results.json are byte-identical between this branch and develop in both modes — the PR changes no migration output.
• -validate diagnostics are identical between the two builds apart from the temporary output-directory prefix (both exit 2 on the same pre-existing diagnostics of the migrated model).

Checklist

• make test and make lint pass locally (make lint: staticcheck on both module roots + gosec, ✓ Lint passed; go test as above)
• Tests added or updated for the change
• Documentation extended where it already covers the surface (see CONTRIBUTING.md)
• Changelog entry added as changes/unreleased/remove-defer-extension.removed.md / .changed.md, not as an edit to CHANGELOG.md
• baselines regenerated and make docs-counts run if a gate count moved (PSSM referee, pilot rejection, pilot differential provenance)
• No internal work-item labels in the body, docs, or changelog

Link to Devin session: https://nasa-jpl-demo.devinenterprise.com/sessions/5a86143306ca4cde86c4dad4e9f9b48a
Open in Devin Desktop: https://nasa-jpl-demo.devinenterprise.com/desktop/session/5a86143306ca4cde86c4dad4e9f9b48a?variant=devin
Requested by: @HuiJun

[devin-ai-integration]

I'll fix CI failures and address comments from users with write access. I'll skip comments containing "(aside)".

• Disable automatic comment, CI, and merge conflict monitoring