[Terastar-Paperclip]

Export canonical output format names so integrations can use Go identifiers instead of string literals when declaring supported codecs. Misspelled constant names then fail compilation, while existing string-based declarations keep working.

Adds FormatMarkdown, FormatJSON, FormatCSV, and CanonicalFormats, and updates the API and integration documentation. Addresses QUA-27.

Validation: go test ./... and go vet ./... in compat; git diff --check.

[Terastar-Paperclip]

Reviewed per Integration & Standards lenses:

• Output shape stability — n/a, no schema/format change; this only adds Go identifiers for existing string literals.
• Backward compatibility — no break. String literals remain valid (SupportsFormat still does exact string comparison against the same literals); this is additive.
• One contract, many implementations — no CONTRACT.md change needed, correctly: the canonical §4 codec names (markdown/json/csv) are unchanged, only how integrators reference them in Go.
• Idiomatic Go — const block + exported var, doc comments updated on Runner.SupportedFormats and SupportsFormat as scoped. go vet/go test both green in CI.

Matches QUA-27 scope and acceptance criteria exactly:

• FormatMarkdown, FormatJSON, FormatCSV, CanonicalFormats exported ✓.
• SupportedFormats and SupportsFormat docs reference the constants ✓.
• compat/README.md "Partial-codec exporters" section updated to recommend constants over bare strings ✓.
• Existing tests still green ✓.

No TestCanonicalFormats tripwire was added — that was explicitly optional in the issue, not required for acceptance. Not a blocker.

I can't submit a GitHub "Approve" review here: CODEOWNERS scopes * to @DTTerastar, and this repo's agents (including me) all push/review under the shared Terastar-Paperclip identity, so GitHub treats any agent approval as self-approval on an already-agent-authored PR. From my side this is ready to merge — needs @DTTerastar's codeowner approval click.