fix(minions): unify JSONB inserts, tighten nullish coalescing

Three non-blocker cleanups from post-ship review of v0.11.0:

- queue.ts add() and completeJob(): pre-stringifying with JSON.stringify
  while other sites pass raw objects with $n::jsonb casts. postgres.js
  double-encodes if you stringify first — works on PGLite (text→JSONB
  auto-cast), fails silently on real PG. Unify on raw object + explicit
  $n::jsonb cast.
- queue.ts readChildCompletions: since clause used sent_at > $2 relying
  on PG's implicit text→TIMESTAMPTZ coercion. Explicit $2::timestamptz
  is safer and clearer.
- types.ts rowToMinionJob: parent_job_id used || which coerces 0 to null.
  Harmless today (SERIAL IDs start at 1) but ?? is semantically correct.

All 110 unit tests pass.

Co-Authored-By: Claude Opus 4.7 <noreply@anthropic.com>

src/core/minions/queue.ts

@@ -113,13 +113,13 @@ export class MinionQueue {
         ? `INSERT INTO minion_jobs (name, queue, status, priority, data, max_attempts, backoff_type,
             backoff_delay, backoff_jitter, delay_until, parent_job_id, on_child_fail,
             depth, max_children, timeout_ms, remove_on_complete, remove_on_fail, idempotency_key)
-           VALUES ($1, $2, $3, $4, $5, $6, $7, $8, $9, $10, $11, $12, $13, $14, $15, $16, $17, $18)
+           VALUES ($1, $2, $3, $4, $5::jsonb, $6, $7, $8, $9, $10, $11, $12, $13, $14, $15, $16, $17, $18)
            ON CONFLICT (idempotency_key) WHERE idempotency_key IS NOT NULL DO NOTHING
            RETURNING *`
         : `INSERT INTO minion_jobs (name, queue, status, priority, data, max_attempts, backoff_type,
             backoff_delay, backoff_jitter, delay_until, parent_job_id, on_child_fail,
             depth, max_children, timeout_ms, remove_on_complete, remove_on_fail, idempotency_key)
-           VALUES ($1, $2, $3, $4, $5, $6, $7, $8, $9, $10, $11, $12, $13, $14, $15, $16, $17, $18)
+           VALUES ($1, $2, $3, $4, $5::jsonb, $6, $7, $8, $9, $10, $11, $12, $13, $14, $15, $16, $17, $18)
            RETURNING *`;
 
       const params = [
@@ -127,7 +127,7 @@ export class MinionQueue {
         opts?.queue ?? 'default',
         childStatus,
         opts?.priority ?? 0,
-        JSON.stringify(data ?? {}),
+        data ?? {},
         opts?.max_attempts ?? 3,
         opts?.backoff_type ?? 'exponential',
         opts?.backoff_delay ?? 1000,
@@ -450,11 +450,11 @@ export class MinionQueue {
       }
 
       const rows = await tx.executeRaw<Record<string, unknown>>(
-        `UPDATE minion_jobs SET status = 'completed', result = $1,
+        `UPDATE minion_jobs SET status = 'completed', result = $1::jsonb,
           finished_at = now(), lock_token = NULL, lock_until = NULL, updated_at = now()
          WHERE id = $2 AND status = 'active' AND lock_token = $3
          RETURNING *`,
-        [result ? JSON.stringify(result) : null, id, lockToken]
+        [result ?? null, id, lockToken]
       );
       if (rows.length === 0) return null;
 
@@ -841,7 +841,7 @@ export class MinionQueue {
     const params: unknown[] = [parentId];
     let sinceClause = '';
     if (opts?.since) {
-      sinceClause = ` AND sent_at > $2`;
+      sinceClause = ` AND sent_at > $2::timestamptz`;
       params.push(opts.since.toISOString());
     }
 

src/core/minions/types.ts

@@ -284,7 +284,7 @@ export function rowToMinionJob(row: Record<string, unknown>): MinionJob {
     lock_token: (row.lock_token as string) || null,
     lock_until: row.lock_until ? new Date(row.lock_until as string) : null,
     delay_until: row.delay_until ? new Date(row.delay_until as string) : null,
-    parent_job_id: (row.parent_job_id as number) || null,
+    parent_job_id: (row.parent_job_id as number | null) ?? null,
     on_child_fail: row.on_child_fail as ChildFailPolicy,
     tokens_input: (row.tokens_input as number) ?? 0,
     tokens_output: (row.tokens_output as number) ?? 0,