chore(spec): regenerate the skill reference index and API-surface snapshot (#3842)

Two more artifacts generated from `packages/spec` and gated in CI, missed
alongside `content/docs/references/`:

- `skills/objectstack-api/references/_index.md` (`check:skill-refs`)
- `packages/spec/api-surface.json` (`check:api-surface`) — records the two
  intentional additions, `HttpStatusErrorCodeMap` and
  `standardErrorCodeForHttpStatus`. 0 breaking, 2 added.

Ran every generate/check pair in the package this time rather than one CI round
at a time: docs, skill-refs, skill-docs, api-surface, spec-changes,
upgrade-guide, react-blocks, authorable-surface, liveness, empty-state,
react-conformance, skill-examples — all twelve pass.

Co-Authored-By: Claude Opus 5 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_018u8vDQLWPJxBWQESznDpSj

Author: claude

packages/spec/api-surface.json

@@ -2627,6 +2627,7 @@
     "HttpFindQueryParamsSchema (const)",
     "HttpMethod (type)",
     "HttpStatusCode (type)",
+    "HttpStatusErrorCodeMap (const)",
     "I18nProtocol (interface)",
     "IMPORT_JOB_MAX_ROWS (const)",
     "IdRequest (type)",
@@ -3081,7 +3082,8 @@
     "WorkflowTransitionResponseSchema (const)",
     "getAuthEndpointUrl (function)",
     "getDefaultRouteRegistrations (function)",
-    "readServiceSelfInfo (function)"
+    "readServiceSelfInfo (function)",
+    "standardErrorCodeForHttpStatus (function)"
   ],
   "./ui": [
     "ACTION_LOCATIONS (const)",

skills/objectstack-api/references/_index.md

@@ -20,7 +20,7 @@ from `node_modules` — there is no local copy in the skill bundle.
 
 ## Transitive dependencies
 
-- `node_modules/@objectstack/spec/src/api/contract.zod.ts` — Standard Create Request
+- `node_modules/@objectstack/spec/src/api/contract.zod.ts` — The numeric HTTP status, when a producer chooses to mirror it into the body.
 - `node_modules/@objectstack/spec/src/api/realtime-shared.zod.ts` — Realtime Shared Protocol
 - `node_modules/@objectstack/spec/src/data/data-engine.zod.ts` — Data Engine Protocol
 - `node_modules/@objectstack/spec/src/data/filter.zod.ts` — Unified Query DSL Specification