feat(tasks): 任务并发上限(可选,超限排队自动补位)

任务页新建任务左侧加「并发设置」齿轮:开关(默认关) + 并发数量(开启默认5)。
开启后新建任务若「运行中」数已达上限,进入「排队中」不启动;有空位时后台
每 5s 自动把最早排队的任务补位启动。

- db: tasks 加持久化 queued 列(schema + ALTER 补旧库);Task.Queued/SetQueued。
- manager: ConcurrencyLimit/SetConcurrency(settings KV);SetTaskQueued(落库+同步内存)。
- 准入与促进器(goals.go):launchTask 统一准入,满则挂起排队;抽出 startTaskEngine
  复用;occupiesSlot/runningTaskCount/queueIfAtCapacity;reconcileConcurrency 每
  scheduler tick 补位(关闭则放行全部排队),concMu 串行化防超发;启动重载/setActive/
  reviveTask 三处'排队则不启动'门。
- settings: /api/settings 增 task_concurrency_enabled/limit;PUT 后立即协调一次。
- web: 齿轮 Dialog(Switch+数量);新增 queued/「排队中」状态(类型/状态色/筛选)。
- 超限只排队新任务,不打断在跑的;排队任务不消耗 LLM(目标拆解推迟到出队)。

go build/vet、tsc 通过;DB queued 往返测试通过。

db/schema.sql

@@ -234,6 +234,7 @@ CREATE TABLE IF NOT EXISTS tasks (
     status         TEXT NOT NULL DEFAULT 'created'
                      CHECK (status IN ('created','running','paused','done','failed','timeout')),
     paused         BOOLEAN NOT NULL DEFAULT false,
+    queued         BOOLEAN NOT NULL DEFAULT false,
     llm_profile_id BIGINT REFERENCES llm_profiles(id) ON DELETE SET NULL,
     company_id     BIGINT REFERENCES companies(id) ON DELETE SET NULL,
     parent_ref     TEXT,
@@ -253,6 +254,8 @@ CREATE TRIGGER trg_tasks_upd BEFORE UPDATE ON tasks
     FOR EACH ROW EXECUTE FUNCTION set_updated_at();
 -- planner 心跳触发间隔(秒);补旧库。默认 300s(5min)。见 docs/planner-trigger-impl-plan.md
 ALTER TABLE tasks ADD COLUMN IF NOT EXISTS plan_heartbeat_seconds INTEGER NOT NULL DEFAULT 300;
+-- 并发上限挂起态;补旧库。true=因并发上限排队、等待空位自动启动。
+ALTER TABLE tasks ADD COLUMN IF NOT EXISTS queued BOOLEAN NOT NULL DEFAULT false;
 
 -- 任务测试范围（资产覆盖度的分母 + 授权边界）。
 --   自动填(source='auto')：insertAssets 顶层按 worker 显式插入的资产类型加保守范围

db/tasks.go

@@ -13,6 +13,7 @@ type Task struct {
 	ExplorationID int64      `json:"exploration_id"`
 	Status        string     `json:"status"`
 	Paused        bool       `json:"paused"`
+	Queued        bool       `json:"queued"` // 因并发上限被挂起、等待空位自动启动;true=尚未开跑
 	LLMProfileID  *int64     `json:"llm_profile_id,omitempty"`
 	ParentRef     string     `json:"parent_ref,omitempty"` // 父任务 id(编排 spawn 记录;空=顶层)
 	CreatedAt     time.Time  `json:"created_at"`
@@ -84,11 +85,11 @@ RETURNING id, status, paused, created_at`, description, goal, expID, llmProfileI
 	return t, tx.Commit()
 }
 
-const taskCols = `id, description, goal, exploration_id, status, paused, llm_profile_id, COALESCE(parent_ref,''), created_at, completed_at, COALESCE(timeout_seconds,0), COALESCE(plan_heartbeat_seconds,300), first_run_at, deadline_at`
+const taskCols = `id, description, goal, exploration_id, status, paused, queued, llm_profile_id, COALESCE(parent_ref,''), created_at, completed_at, COALESCE(timeout_seconds,0), COALESCE(plan_heartbeat_seconds,300), first_run_at, deadline_at`
 
 func scanTask(sc interface{ Scan(...any) error }) (*Task, error) {
 	var t Task
-	if err := sc.Scan(&t.ID, &t.Description, &t.Goal, &t.ExplorationID, &t.Status, &t.Paused, &t.LLMProfileID, &t.ParentRef, &t.CreatedAt, &t.CompletedAt, &t.TimeoutSeconds, &t.PlanHeartbeatSeconds, &t.FirstRunAt, &t.DeadlineAt); err != nil {
+	if err := sc.Scan(&t.ID, &t.Description, &t.Goal, &t.ExplorationID, &t.Status, &t.Paused, &t.Queued, &t.LLMProfileID, &t.ParentRef, &t.CreatedAt, &t.CompletedAt, &t.TimeoutSeconds, &t.PlanHeartbeatSeconds, &t.FirstRunAt, &t.DeadlineAt); err != nil {
 		return nil, err
 	}
 	return &t, nil
@@ -136,6 +137,13 @@ func (d *DB) SetPaused(id int64, paused bool) error {
 	return err
 }
 
+// SetQueued persists a task's queued flag (并发上限挂起态). A queued task is held
+// (engine not started) until the concurrency reconciler promotes it into a free slot.
+func (d *DB) SetQueued(id int64, queued bool) error {
+	_, err := d.Exec(`UPDATE tasks SET queued=$1 WHERE id=$2`, queued, id)
+	return err
+}
+
 // SetStatus updates a task's lifecycle status. Entering a terminal state
 // (done/failed/timeout) stamps completed_at once (COALESCE keeps the first stamp
 // stable); moving back to a non-terminal state clears it, so a re-run has no stale

db/tasks_test.go

@@ -27,6 +27,23 @@ func TestTaskLifecycleAndDeleteCascade(t *testing.T) {
 	if err != nil || got == nil || !got.Paused {
 		t.Fatalf("paused not persisted: %+v err=%v", got, err)
 	}
+	if got.Queued {
+		t.Fatalf("new task should not be queued: %+v", got)
+	}
+
+	// queued (concurrency-hold) flag round-trips independently of paused
+	if err := d.SetQueued(tk.ID, true); err != nil {
+		t.Fatal(err)
+	}
+	if g, _ := d.GetTask(tk.ID); g == nil || !g.Queued {
+		t.Fatalf("queued not persisted: %+v", g)
+	}
+	if err := d.SetQueued(tk.ID, false); err != nil {
+		t.Fatal(err)
+	}
+	if g, _ := d.GetTask(tk.ID); g == nil || g.Queued {
+		t.Fatalf("queued not cleared: %+v", g)
+	}
 
 	// list contains it
 	list, _ := d.ListTasks()