feat(reporting): add @spine and measure @default for FR-044

.claude/rules/cross-language-porting.md

@@ -17,7 +17,7 @@ Preserve the following contracts exactly across all language ports:
 
 **Metamodel subtype vocabularies (must be identical across languages):** the `registry-conformance` gate (`fixtures/registry-conformance/`) is the structural enforcer of this rule — each port emits its registry as a canonical manifest byte-matched to `expected-registry.json`. **All five ports (TS / C# / Java / Kotlin / Python) are live + green** (SP-G Java/Kotlin reconciliation complete; the JVM runners compose from the defined metamodel provider set so codegen-base/om classpath SPI does not pollute the measured vocabulary). See `fixtures/registry-conformance/README.md`.
 - Filter operators: `eq`, `ne`, `gt`, `gte`, `lt`, `lte`, `in`, `like`, `isNull`
-- Object subtypes: `entity` (owns data: own identity, writable sources, lifecycle), `value` (pure shape: NO identity, NO source, ever; constructed — by caller/embedding — never populated; may `extends` entity fields for shape; a value-hosted field may carry `origin.passthrough` but never an assembly origin), `projection` (derived read-only representation: fields `extends`-bound / origin-derived / self-declared-under-external-assembly, all read-only at subtype level; identity optional and MUST extend an entity identity; sources restricted to read-only `@kind`s; the declared field set IS the exposure — inclusive list, fail-closed). A field carrying `origin.*` is derived ⇒ read-only wherever it lives (incl. on entities). An entity's primary source must be a writable `@kind` (read-only kinds only in read role). See [ADR-0028](spec/decisions/ADR-0028-object-taxonomy-projection-value-purity.md). (FR-024 Phase E — `object.projection`/`value` are registered in `expected-registry.json` and the projection/value validation passes [identity pass-through, value-purity, projection-licensing, `@via` inference/cardinality, extends/origin agreement, derived-field providability] are enforced cross-port in all 5 ports. The **B4b** entity-primary-source-readonly cutover [the "writable `@kind`" clause above — `ERR_ENTITY_PRIMARY_SOURCE_READONLY`] + the projection codegen fan-out (read-only DTOs for view-kind projections; FR-015 proc-callables for proc-kind projections in TypeScript, C# and Kotlin ONLY — Java and Python ship no callable generator at all, so the cross-port claim does NOT cover that clause; api-docs label `object.projection` units as `projection` and document their generated `<Name>Dto`) are now shipped cross-port; the remaining FR-024 work is the declared-API surface — tracked in #10.) **`report` (FR-044 Plan 1)** is a root object subtype registered in all five ports, with the `dimension.attribute` / `dimension.time` / `measure.aggregate` / `measure.ratio` / `segment.filter` children on `object.entity` and the relative-date filter value — loader-validated (`ERR_INVALID_DIMENSION` / `ERR_INVALID_MEASURE` / `ERR_INVALID_REPORT` / `ERR_REPORT_FOREIGN_MEASURE`, plus `ERR_BAD_ATTR_FILTER` for relative dates off a reporting host) and, since FR-044 Plan 2, **lowered only when it declares a read-only `source.rdb` of `@kind: view`**: `meta migrate` creates that view (TypeScript only, ADR-0015), every port reads it (persistence corpus, `report-shapes.json`), C# generates its typed row and Kotlin its Exposed table object, and, since FR-044 Plan 3, every port's generators **serve it as a keyless read-only projection** (GET list with filter/sort/paging on every derived field that has a filter band, `POST` 405, no `/{id}`; row type + filter allowlist + route/controller per port, gated by the api-contract `report/` sub-corpus in the generated lane). The client UI tier (hooks, grids, forms) and a report with no view source at all stay inert, gated by the 27 `reporting` conformance fixtures and the `codegen-noop` corpus. A served report is the predicate `servedReport` (TS) / `ReportRows.IsViewBacked` (C#) / `RestSurfaceGate.isServedReport` (Java, Kotlin) / `is_served_report` (Python): concrete, read source `@kind: view`. See [docs/features/reporting.md](docs/features/reporting.md).
+- Object subtypes: `entity` (owns data: own identity, writable sources, lifecycle), `value` (pure shape: NO identity, NO source, ever; constructed — by caller/embedding — never populated; may `extends` entity fields for shape; a value-hosted field may carry `origin.passthrough` but never an assembly origin), `projection` (derived read-only representation: fields `extends`-bound / origin-derived / self-declared-under-external-assembly, all read-only at subtype level; identity optional and MUST extend an entity identity; sources restricted to read-only `@kind`s; the declared field set IS the exposure — inclusive list, fail-closed). A field carrying `origin.*` is derived ⇒ read-only wherever it lives (incl. on entities). An entity's primary source must be a writable `@kind` (read-only kinds only in read role). See [ADR-0028](spec/decisions/ADR-0028-object-taxonomy-projection-value-purity.md). (FR-024 Phase E — `object.projection`/`value` are registered in `expected-registry.json` and the projection/value validation passes [identity pass-through, value-purity, projection-licensing, `@via` inference/cardinality, extends/origin agreement, derived-field providability] are enforced cross-port in all 5 ports. The **B4b** entity-primary-source-readonly cutover [the "writable `@kind`" clause above — `ERR_ENTITY_PRIMARY_SOURCE_READONLY`] + the projection codegen fan-out (read-only DTOs for view-kind projections; FR-015 proc-callables for proc-kind projections in TypeScript, C# and Kotlin ONLY — Java and Python ship no callable generator at all, so the cross-port claim does NOT cover that clause; api-docs label `object.projection` units as `projection` and document their generated `<Name>Dto`) are now shipped cross-port; the remaining FR-024 work is the declared-API surface — tracked in #10.) **`report` (FR-044 Plan 1)** is a root object subtype registered in all five ports, with the `dimension.attribute` / `dimension.time` / `measure.aggregate` / `measure.ratio` / `segment.filter` children on `object.entity` and the relative-date filter value — loader-validated (`ERR_INVALID_DIMENSION` / `ERR_INVALID_MEASURE` / `ERR_INVALID_REPORT` / `ERR_REPORT_FOREIGN_MEASURE`, plus `ERR_BAD_ATTR_FILTER` for relative dates off a reporting host) and, since FR-044 Plan 2, **lowered only when it declares a read-only `source.rdb` of `@kind: view`**: `meta migrate` creates that view (TypeScript only, ADR-0015), every port reads it (persistence corpus, `report-shapes.json`), C# generates its typed row and Kotlin its Exposed table object, and, since FR-044 Plan 3, every port's generators **serve it as a keyless read-only projection** (GET list with filter/sort/paging on every derived field that has a filter band, `POST` 405, no `/{id}`; row type + filter allowlist + route/controller per port, gated by the api-contract `report/` sub-corpus in the generated lane). The client UI tier (hooks, grids, forms) and a report with no view source at all stay inert, gated by the 37 `reporting` conformance fixtures and the `codegen-noop` corpus. A served report is the predicate `servedReport` (TS) / `ReportRows.IsViewBacked` (C#) / `RestSurfaceGate.isServedReport` (Java, Kotlin) / `is_served_report` (Python): concrete, read source `@kind: view`. See [docs/features/reporting.md](docs/features/reporting.md).
 - Source subtypes: `rdb` (paradigm; ADR-0007). The pre-v2 `dbTable`/`dbView` subtypes are RETIRED — `source.rdb` + `@kind: table|view|materializedView|storedProc|tableFunction` is the form, with read-only-ness derived from `@kind`. Multi-source via `@role` (exactly one `primary` per object). Source physical name = `@table` (NOT `@name`); field physical name = `@column` (renamed from `@dbColumn`). Referential actions on relationships: `@onDelete` / `@onUpdate`.
 - Origin subtypes: `passthrough`, `aggregate`, `collection`, `computed`, `first` (concrete; `base` is the abstract root). `passthrough` is legal on an `object.value`-hosted field (FR-015 parameter lineage); the four assembly origins (`aggregate`/`computed`/`collection`/`first`) live on `object.projection` only — a value-hosted assembly origin is `ERR_SUBTYPE_RULE_VIOLATION` (#210).
 - Relationship subtypes: `association`, `aggregation`, `composition`. Cardinality via `@cardinality: one|many`; target via `@objectRef`. **M:N (FR-018) slim vocabulary:** `@cardinality: "many"` + `@objectRef` (target) + `@through` (the junction/through entity — a third entity that MUST declare two `identity.reference` children, one per FK side). The relationship's FK fields are **derived** from those references (the `identity.reference` SSOT for FK direction), never restated. `@sourceRefField` (optional) disambiguates a *directed* self-join by naming the source-side FK field on the junction (the other reference is the target side); on a `@cardinality: one` relationship it instead names which of several `identity.reference` nodes onto the same target this relationship navigates, short-circuiting the unique-candidate/`@sourceRefField`/name-pairing ladder (#368, [ADR-0029](spec/decisions/ADR-0029-entity-child-extends-and-via-inference.md) Amendment 1) — an unresolvable 1:N reference set is `ERR_INVALID_RELATIONSHIP` at load. `@symmetric` (optional boolean) marks an *undirected* self-join (union-on-read) — valid only when `@objectRef` == the declaring entity, and mutually exclusive with `@sourceRefField`. The pre-FR-018 `@joinEntity`/`@joinFields` attrs are REMOVED. Validation errors: symmetric-on-hetero / symmetric+sourceRefField → `ERR_BAD_ATTR_VALUE`; junction-missing-two-references / sourceRefField-not-matching / M:N-attr-on-1:N / **junction-unpairable** → `ERR_INVALID_RELATIONSHIP`. **Unpairable means the junction declares its two references but neither resolves to the navigating entity, or neither to the `@objectRef` target** — declaring two references is NOT enough, and the loader now checks WHAT they point at (owner ruling 2026-09-20). It does so by running the real FK derivation and converting its failure, never a parallel re-implementation, so the loader and the derivation cannot drift; scope mirrors codegen's own iteration exactly — every CONCRETE, non-projection object crossed with its EFFECTIVE relationships, NOT deduped by declaration, because pairing is a property of the navigating entity and an inherited M:N can pair from one subtype and not another. Before the ruling this loaded clean and then diverged: TS and C# warned and emitted no traversal route (a silent 404), while Java, Kotlin and Python failed the build. Gated by `fixtures/conformance/error-relationship-m2m-junction-unpairable/`.