Document that publicSurface: off does not suppress either check-run

[JSONbored]

Context

publicSurface (src/types.ts:947, no doc comment) governs only shouldPublishPrComment/shouldApplyPrLabel (comment + label). Neither the Context check (checkRunMode) nor the Gate check (reviewCheckMode) is ANDed with it — confirmed end-to-end at src/queue/processors.ts:9603 and :7487. This is intentional and partially documented elsewhere, not an accidental bug: processors.ts:7518-7525 explicitly cites #2852 ("the two are now independent axes"), and src/signals/registration-readiness.ts:138-139 already surfaces "Gittensory stays quiet... with the opt-in gate check still enabled" in the maintainer-facing readiness report. Requires a non-default combination to trigger (checkRunMode/reviewCheckMode default off; publicSurface defaults to comment_and_label), and check-run content is intentionally minimal/non-sensitive — no data-leak angle, only maintainer-surprise risk.

Requirements

• Docs-only, no behavior change — current behavior is load-bearing per feat(selfhost): configurable review-check publish mode (required/visible/disabled) #2852 (the check-run must keep posting for branch-protection/auto-merge to keep working).

Deliverables

• Add a doc comment above publicSurface (types.ts:947) stating it governs ONLY the PR comment and label, cross-referencing checkRunMode and reviewCheckMode as the separate switches needed for full silence.
• Add the same .describe() caveat to the four publicSurface: z.enum(...) occurrences in src/openapi/schemas.ts (lines 782, 862, 1261, 2176).
• Run npm run ui:openapi after the schema change.

Expected Outcome

A maintainer reading publicSurface's doc or the OpenAPI schema understands it does not silence the check-runs.

Links & Resources

• Evidence: src/types.ts:947; src/signals/settings-preview.ts:24-26,28-38,91-114; src/queue/processors.ts:9603,7487,7518-7525; src/signals/registration-readiness.ts:138-139

---

Part of #5270 (roadmap epic).

[linear-code]

JSO-3780