feat(fleet): native Mosaic backlog on @mosaicstack/db (atomic claim + TTL) (#657)

packages/db/src/schema.ts

@@ -587,6 +587,62 @@ export const summarizationJobs = pgTable(
   (t) => [index('summarization_jobs_status_idx').on(t.status)],
 );
 
+// ─── Fleet Backlog ────────────────────────────────────────────────────────────
+// Mosaic-native backlog-of-record (card A4). This REPLACES the former Hermes
+// adapter — there is NO runtime dependency on Hermes. Cards form a dependency
+// DAG (`depends_on`), are claimed atomically by fleet workers via
+// `SELECT ... FOR UPDATE SKIP LOCKED`, and auto-expire via a TTL so a crashed
+// claimer's card returns to the pool.
+
+/**
+ * Lifecycle status of a backlog card.
+ * - ready:   eligible to be claimed (once its deps are all `done`).
+ * - claimed: a worker holds it (claim_owner + claimed_at set); may expire via TTL.
+ * - blocked: explicitly parked; never auto-claimed.
+ * - done:    completed; satisfies dependents.
+ */
+export const backlogStatusEnum = pgEnum('backlog_status', ['ready', 'claimed', 'blocked', 'done']);
+
+export const backlog = pgTable(
+  'backlog',
+  {
+    /** Stable, caller-supplied card id (e.g. "A4", "fleet-001"). PK. */
+    id: text('id').primaryKey(),
+    title: text('title').notNull(),
+    body: text('body'),
+    /** Board/phase grouping (e.g. "M1", "fleet"). Free-form. */
+    phase: text('phase'),
+    /** Higher number = higher priority; claim picks the max-priority ready card. */
+    priority: integer('priority').notNull().default(0),
+    status: backlogStatusEnum('status').notNull().default('ready'),
+    /** DAG edges: ids of cards this one depends on. "ready" requires all done. */
+    dependsOn: jsonb('depends_on').notNull().$type<string[]>().default([]),
+    /** Owner token of the current claim (worker/agent id). NULL when unclaimed. */
+    claimOwner: text('claim_owner'),
+    /** TTL of the active claim in seconds. NULL when unclaimed. */
+    claimTtlSeconds: integer('claim_ttl_seconds'),
+    /** When the active claim was taken. NULL when unclaimed. claimed_at + ttl = expiry. */
+    claimedAt: timestamp('claimed_at', { withTimezone: true }),
+    /** Count of times this card has been claimed (incremented on each claim). */
+    attempts: integer('attempts').notNull().default(0),
+    /** Optional dedup key for `create`; a repeat key returns the existing card. */
+    idempotencyKey: text('idempotency_key'),
+    /** Acceptance criteria — free-form JSON (array of strings or object). */
+    acceptance: jsonb('acceptance'),
+    createdAt: timestamp('created_at', { withTimezone: true }).notNull().defaultNow(),
+    updatedAt: timestamp('updated_at', { withTimezone: true }).notNull().defaultNow(),
+  },
+  (t) => [
+    // Hot path: claim scans ready cards ordered by priority then age.
+    index('backlog_status_priority_idx').on(t.status, t.priority),
+    // reclaim sweeps claimed cards by claimed_at to find expired ones.
+    index('backlog_status_claimed_at_idx').on(t.status, t.claimedAt),
+    // Idempotent create dedups on this key (NULLs are distinct in Postgres, so
+    // many unkeyed cards coexist; a repeated non-null key collides).
+    uniqueIndex('backlog_idempotency_key_idx').on(t.idempotencyKey),
+  ],
+);
+
 // ─── Federation ──────────────────────────────────────────────────────────────
 // Enums declared before tables that reference them.
 // All federation definitions live in this file (avoids CJS/ESM cross-import