perf(postgres): 回收突发连接并等待验收副作用

失败 Run 的未提交任务已取消，但退款 outbox 尚未完成时下一轮会继承 API 连接高水位和 canceled acquire 增量，污染容量验收。

新增 AI_GATEWAY_DATABASE_MAX_CONN_IDLE_SECONDS，生产配置 30 秒回收突发空闲连接；验收中止后等待旧任务、退款、回调和数据库连接全部收敛后才允许新负载启动。

验证：Go 全量测试、gofmt、bash -n、ShellCheck、kubectl kustomize 和 git diff --check 通过。

scripts/cluster/run-production-acceptance.sh

@@ -226,21 +226,41 @@ wait_for_existing_tasks_to_drain() {
 
 wait_for_terminal_acceptance_tasks_to_drain() {
   local deadline=$((SECONDS + 300))
-  local active
+  local state active side_effects connections max_connections
   while (( SECONDS < deadline )); do
-    active=$(database_query "
-SELECT count(*)
-FROM gateway_tasks task
-JOIN gateway_acceptance_runs run ON run.id=task.acceptance_run_id
-WHERE run.status IN ('failed', 'aborted')
-  AND task.status IN ('queued', 'running');")
-    if [[ $active == 0 ]]; then
+    state=$(database_query "
+SELECT
+  (SELECT count(*)
+   FROM gateway_tasks task
+   JOIN gateway_acceptance_runs run ON run.id=task.acceptance_run_id
+   WHERE run.status IN ('failed', 'aborted')
+     AND task.status IN ('queued', 'running'))||','||
+  (
+    (SELECT count(*)
+     FROM settlement_outbox settlement
+     JOIN gateway_tasks task ON task.id=settlement.task_id
+     JOIN gateway_acceptance_runs run ON run.id=task.acceptance_run_id
+     WHERE run.status IN ('failed', 'aborted')
+       AND settlement.status IN ('pending', 'processing', 'retryable_failed'))
+    +
+    (SELECT count(*)
+     FROM gateway_task_callback_outbox callback
+     JOIN gateway_tasks task ON task.id=callback.task_id
+     JOIN gateway_acceptance_runs run ON run.id=task.acceptance_run_id
+     WHERE run.status IN ('failed', 'aborted')
+       AND callback.status <> 'delivered')
+  )||','||
+  (SELECT count(*) FROM pg_stat_activity WHERE backend_type='client backend')||','||
+  (SELECT setting FROM pg_settings WHERE name='max_connections');")
+    IFS=',' read -r active side_effects connections max_connections <<<"$state"
+    if [[ $active == 0 && $side_effects == 0 ]] &&
+      (( connections * 2 < max_connections )); then
       return 0
     fi
-    echo "waiting_for_terminal_acceptance_tasks=$active"
+    echo "waiting_for_terminal_acceptance_tasks=$active side_effects=$side_effects database_connections=$connections"
     sleep 2
   done
-  echo "terminal acceptance tasks did not drain within 5 minutes: active=$active" >&2
+  echo "terminal acceptance state did not drain within 5 minutes: active=$active side_effects=$side_effects database_connections=$connections" >&2
   return 1
 }
 
@@ -675,6 +695,7 @@ apply_capacity_profile() {
   local slots pool media global
   local api_pool=$AI_GATEWAY_ACCEPTANCE_API_DATABASE_MAX_CONNS
   local min_idle=4
+  local max_idle_seconds=30
   case $profile in
     P24) slots=24; pool=32; media=24; global=48 ;;
     P28) slots=28; pool=36; media=28; global=56 ;;
@@ -688,6 +709,7 @@ apply_capacity_profile() {
       "AI_GATEWAY_ASYNC_WORKER_HARD_LIMIT=$global" \
       "AI_GATEWAY_DATABASE_MAX_CONNS=$pool" \
       "AI_GATEWAY_DATABASE_MIN_IDLE_CONNS=$min_idle" \
+      "AI_GATEWAY_DATABASE_MAX_CONN_IDLE_SECONDS=$max_idle_seconds" \
       "AI_GATEWAY_MEDIA_MATERIALIZATION_CONCURRENCY=$media" \
       "AI_GATEWAY_MEDIA_REQUEST_CONCURRENCY=$media" >/dev/null
     remote_kubectl rollout status "deployment/easyai-worker-$site" \
@@ -695,7 +717,8 @@ apply_capacity_profile() {
     remote_kubectl set env "deployment/easyai-api-$site" -n "$namespace" \
       "AI_GATEWAY_ASYNC_WORKER_HARD_LIMIT=$global" \
       "AI_GATEWAY_DATABASE_MAX_CONNS=$api_pool" \
-      "AI_GATEWAY_DATABASE_MIN_IDLE_CONNS=$min_idle" >/dev/null
+      "AI_GATEWAY_DATABASE_MIN_IDLE_CONNS=$min_idle" \
+      "AI_GATEWAY_DATABASE_MAX_CONN_IDLE_SECONDS=$max_idle_seconds" >/dev/null
     remote_kubectl rollout status "deployment/easyai-api-$site" \
       -n "$namespace" --timeout=300s
   done