docs(api): correct /docs/api against the v1 implementation (#999)

Audited every endpoint, param, header, request/response field, error code, and
webhook event in the public API docs against the v1 implementation and fixed the
drift; addressed two rounds of CodeRabbit review.

- Error envelope, idempotency, dry-run, and reversal-field corrections.
- Registered the missing articles/dimensions/inbox-items reference resources.
- Cookbook fixes: removed nonexistent endpoints, corrected params/fields, fixed
  the test-key vs live-key quickstart flow and the year-end lock/close sequence.
- Webhooks/changelog: retry window ~87h (incl. route metadata), shipped-vs-
  coming-soon, counts, API-key format, previous_attributes.
- export-docs-to-website.mts absolutises app-served links for the website.

The gnubok-website side is on branch docs/api-correctness (already deployed).

🤖 Generated with [Claude Code](https://claude.com/claude-code)

app/api/v1/companies/[companyId]/webhooks/[id]/test/route.ts

@@ -32,7 +32,7 @@ registerEndpoint({
   doNotUseFor:
     'Smoke-testing the dispatcher itself (use a real event). Replaying a failed delivery (use POST /webhook-deliveries/{id}/retry).',
   pitfalls: [
-    'Test deliveries follow the same retry policy as real events: a 500 from your receiver will retry 7 times over ~72h. Use a 2xx ack-only handler if you want a clean signal.',
+    'Test deliveries follow the same retry policy as real events: a 500 from your receiver will retry 7 times over ~87h (about 3.6 days). Use a 2xx ack-only handler if you want a clean signal.',
   ],
   example: {
     response: {

app/api/v1/operations/[id]/route.ts

@@ -46,7 +46,7 @@ registerEndpoint({
   description:
     'Returns the current snapshot of a v1 async operation: status (queued / running / succeeded / failed / cancelled), progress (jsonb, free-form), result (on success), and error (on failure). The operation_id is returned by the POST endpoints that initiate async work (period close, year-end, currency revaluation, SIE import).',
   useWhen:
-    'You started an async operation and need to know whether it has finished. Poll every 5-30 seconds; switch to the `operation.completed` webhook for production integrations.',
+    'You started an async operation and need to know whether it has finished. Poll every 5-30 seconds until a terminal status. (The 202 response advertises `operation.completed` as the eventual push signal, but that webhook event is not deliverable yet — polling is the only supported completion signal today.)',
   doNotUseFor:
     'Fetching the resource the operation produced: once status=succeeded, read the result field or call the resource-specific GET endpoint. Cancelling a running operation (no cancel endpoint exists in v1).',
   pitfalls: [