feat(server): W2-B sources, identity resolution, metadata and site workbench

- Sites / accounts / feeds: registry view (/site-definitions), site CRUD with
  enable/disable (history stays queryable, marked site_disabled), accounts and
  feed URLs stored as secrets (only secret_ref / redacted urlDisplay exposed),
  feed enable/disable/reset/fetch; one shared rate limiter + adapter per site.
- Tasks: ingestFeed (FeedFetchState/FeedCursor on feed_source, observation
  feed+guid upsert with digest-change updates, source_release site+id
  aggregation across feeds, auth failure -> account invalid + decision, no
  retry, gap -> feed.gap_suspected -> budgeted backfill snapshot),
  resolveObservation (parseRelease -> local recall via title_alias pg_trgm +
  accepted identities -> TMDB -> resolveIdentity; auto binds entity /
  provisional units / identities / aliases, otherwise identity_candidate pool
  with evidence version and bounded review backoff; manual lock respected),
  refreshMetadata (metadata_field + field_override, user locks win, paths
  untouched), snapshotSite (site_snapshot coverage records).
- Events: feed.due, feed.gap_suspected, release.observed (self-consumed),
  release.resolved, decision.created/updated; scheduler in worker start().
- Identity API: entity detail with redirects, manual mapping correction with
  identity_revision, merge with identity_redirect, pool list/assign/dismiss/
  retry, content unit numbering lock, aliases, external identities.
- Decisions: list/summary (by entity and kind)/detail/resolve; identity
  options executed directly.
- Workbench: /sites/{id}/releases (snapshot first, coalesced live search with
  backoff, origin + freshness) and /sites/{id}/releases/{rid} (volatile field
  recheck times, refresh keeps data on failure).
- Capabilities: catalog.lookup, release.search, release.inspect,
  identity.resolve.
- Migrations 0018-0020: site.adapter api, source_release.resolution_locked,
  site_snapshot, identity_candidate, resolution_attempt, identity_redirect,
  metadata_field, field_override.

Co-Authored-By: Claude Opus 5.5 <[email protected]>

packages/db/test/schema.test.ts

@@ -68,6 +68,13 @@ const EXPECTED_TABLES = [
   "tasks_fact",
   "tasks_op_ledger",
   "agent_run_event",
+  // W2-B 来源/身份/元数据(0018–0020)
+  "site_snapshot",
+  "identity_candidate",
+  "resolution_attempt",
+  "identity_redirect",
+  "metadata_field",
+  "field_override",
   // 登录门禁(0015)与 SSE 多进程总线(0016)
   "admin_user",
   "admin_session",