fix(routing): 修正 Worker 心跳时间查询

生产 shadow 发布证明 PostgreSQL 将未显式定型的时间参数推断为 interval，导致 Worker 列表和容量查询返回 SQLSTATE 42883。

改为在 Go 中计算心跳截止时间并以 timestamptz 参数查询，补充真实 PostgreSQL 集成回归。

apps/api/internal/store/execution_pools.go

@@ -101,14 +101,15 @@ func (s *Store) ListWorkers(ctx context.Context, now time.Time) ([]executionpool
 	if now.IsZero() {
 		now = time.Now()
 	}
+	cutoff := now.Add(-workerHeartbeatStaleAfter)
 	rows, err := s.pool.Query(ctx, `
 SELECT worker_id, instance_id, pool_id, endpoint, protocol_version, revision,
        capabilities, allocated_capacity, safe_capacity, heavy_capacity,
        active_tasks, pressure_state, heartbeat_at, load_sampled_at
 FROM gateway_worker_instances
 WHERE status = 'active'
-  AND heartbeat_at > $1 - $2::interval
+  AND heartbeat_at > $1::timestamptz
-ORDER BY pool_id, instance_id`, now, workerHeartbeatStaleAfter.String())
+ORDER BY pool_id, instance_id`, cutoff)
 	if err != nil {
 		return nil, err
 	}
@@ -346,6 +347,7 @@ func (s *Store) ListCapacity(ctx context.Context, now time.Time) ([]executionpoo
 	if now.IsZero() {
 		now = time.Now()
 	}
+	cutoff := now.Add(-workerHeartbeatStaleAfter)
 	rows, err := s.pool.Query(ctx, `
 SELECT pool.pool_id,
        COUNT(worker.instance_id)::int,
@@ -360,10 +362,10 @@ FROM gateway_execution_pools pool
 LEFT JOIN gateway_worker_instances worker
  ON worker.pool_id = pool.pool_id
  AND worker.status = 'active'
- AND worker.heartbeat_at > $1 - $2::interval
+ AND worker.heartbeat_at > $2::timestamptz
 WHERE pool.state = 'active'
 GROUP BY pool.pool_id
-ORDER BY pool.pool_id`, now, workerHeartbeatStaleAfter.String())
+ORDER BY pool.pool_id`, now, cutoff)
 	if err != nil {
 		return nil, err
 	}

apps/api/internal/store/execution_pools_integration_test.go

@@ -0,0 +1,20 @@
+package store
+
+import (
+	"context"
+	"testing"
+	"time"
+)
+
+func TestExecutionPoolQueriesUseTimestampCutoff(t *testing.T) {
+	db := billingV2IntegrationStore(t)
+	ctx, cancel := context.WithTimeout(context.Background(), 10*time.Second)
+	defer cancel()
+
+	if _, err := db.ListWorkers(ctx, time.Now()); err != nil {
+		t.Fatalf("list workers with timestamp cutoff: %v", err)
+	}
+	if _, err := db.ListCapacity(ctx, time.Now()); err != nil {
+		t.Fatalf("list capacity with timestamp cutoff: %v", err)
+	}
+}