feat(server): W4-A integration endpoints and contract gaps

- POST /acquisition-plans: manual submit via download.plan -> download.submit
  (same authorization/audit/idempotency path as the agent), slotId or entityId
- read-only /media-assets, /asset-locations, /asset-unit-coverage, /path-bindings,
  /reconcile-runs, /server-mappings, /artifacts, GET /title-aliases/{id};
  unimplemented write endpoints removed from api.ts; registry test now checks both directions
- candidate evaluation upsert per (slot, source_release) + migration 0022 dedupe/unique index
- organization records expose downloadTaskId (+ list filter); inventory adds
  subscribed/candidateReasons; feed sources expose derived possibleGap
- GET /events?after=&limit= JSON replay page for API key callers (same sse_event table)
- preference tag revision history from audit_event; subscriptions/identities/aliases
  lists carry mediaEntityTitle; subscription q/mediaKind search; slot subscriptionId
  filter + currentAsset summary; policy preview samples carry title/reasons
- DecisionSummary, IdentityRevisionList, ReleaseIdentityResult, PolicyPreviewSummary exported from contracts

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

packages/contracts/src/sources.ts

@@ -105,6 +105,13 @@ export const FeedSource = EntityBase.extend({
   backoffUntil: Timestamp.nullable(),
   healthStatus: FeedHealth,
   lastError: JsonObject.nullable(),
+  /**
+   * 派生字段(非表列):最近一次抓取发现与上次窗口零重叠 → 疑似漏项,已排站点补漏。
+   * 下一次抓取窗口重新衔接后清空。站点未登记的 Feed 无法补漏(backfillQueued=false)。
+   */
+  possibleGap: z
+    .object({ detectedAt: Timestamp, previousFetchedAt: Timestamp.nullable(), backfillQueued: z.boolean() })
+    .nullable(),
 });
 export type FeedSource = z.infer<typeof FeedSource>;
 /** url 为只写明文(可能含 passkey),服务端加密存为 secret 并生成 urlDisplay */