feat: 编排器跨项目全局并发上限闸（tsk_erQHNYdn6i9g）

新增用户级设置项 globalConcurrency（settings 表，独立于新建项目默认值
来源 concurrency），缺省 0 = 不限，向后兼容无需 DB 迁移。

- store: UserSettings 加 globalConcurrency 字段 + 默认 0；新增
  globalInflightCount()（跨所有项目 started run 总数，与 inflightTaskIds 同口径）
- orchestrator.claimTick: 叠加全局闸，与 per-project 闸串联（都过才领）；
  轮初查一次全局在途、轮内手动 ++，达上限即 return 跨所有项目停止领取
- api: PUT /api/settings 支持 globalConcurrency（空/null 归一为 0）
- web: 侧栏「全局设置」入口 + 模态，编辑/回显/校验（≥0 整数）
- test: 新增全局闸达上限跨项目阻止 / 未达上限正常领取 / 边界 / 轮初短路 用例

Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>

test/orchestrator.test.ts

@@ -443,6 +443,69 @@ test('auto-easy 不做规划：medium(speccing) 不被领取', () => {
   store.close();
 });
 
+// ───────────────────────── 全局并发闸（跨项目在途总数上限）─────────────────────────
+
+/** 单 store 建两个 active / auto-easy 项目，各塞 n 个 easy 任务，per-project 并发足够大（不成为瓶颈）。 */
+function setupTwoProjects(n = 2, concurrency = 5): { store: Store; p1: string; p2: string } {
+  const store = new Store(':memory:');
+  const p1 = store.createProject({ name: 'g1', repoPath: '/tmp/g1-' + Math.random(), autonomy: 'auto-easy', concurrency });
+  const p2 = store.createProject({ name: 'g2', repoPath: '/tmp/g2-' + Math.random(), autonomy: 'auto-easy', concurrency });
+  for (let i = 0; i < n; i++) {
+    store.createTask({ projectId: p1.id, title: `p1-${i}`, complexity: 'easy' });
+    store.createTask({ projectId: p2.id, title: `p2-${i}`, complexity: 'easy' });
+  }
+  return { store, p1: p1.id, p2: p2.id };
+}
+
+test('全局闸：globalConcurrency=1 达上限 → 跨所有项目只领一个（per-project 闸都没满也阻止）', () => {
+  const { store } = setupTwoProjects(2, 5);
+  store.putSettings({ globalConcurrency: 1 });
+  const state = freshState();
+  const { deps } = mockDeps(state);
+  createOrchestrator(store, noopLog, deps).claimTick();
+  assert.equal(state.spawned.length, 1, '全局闸=1：两项目共 4 个可领任务，本轮只放一个');
+  store.close();
+});
+
+test('全局闸：globalConcurrency=0（缺省）不限 → 两项目任务全领（不误伤）', () => {
+  const { store, p1, p2 } = setupTwoProjects(2, 5);
+  // 不设 globalConcurrency（默认 0）
+  assert.equal(store.getSettings().globalConcurrency, 0);
+  const state = freshState();
+  const { deps } = mockDeps(state);
+  createOrchestrator(store, noopLog, deps).claimTick();
+  assert.equal(state.spawned.length, 4, '不限：两项目各 2 个共 4 个全部领取');
+  assert.equal(store.listTasks(p1).filter((t) => t.status === 'executing').length, 2);
+  assert.equal(store.listTasks(p2).filter((t) => t.status === 'executing').length, 2);
+  store.close();
+});
+
+test('全局闸：globalConcurrency=3 两项目共 4 任务 → 一轮恰好领 3（边界）', () => {
+  const { store } = setupTwoProjects(2, 5);
+  store.putSettings({ globalConcurrency: 3 });
+  const state = freshState();
+  const { deps } = mockDeps(state);
+  createOrchestrator(store, noopLog, deps).claimTick();
+  assert.equal(state.spawned.length, 3, '全局闸=3：达上限即跨项目停止，恰好领 3 个');
+  store.close();
+});
+
+test('全局闸：在途已达上限 → 整轮直接不领（轮初短路）', () => {
+  const { store, p1 } = setupTwoProjects(2, 5);
+  store.putSettings({ globalConcurrency: 1 });
+  const state = freshState();
+  const { deps } = mockDeps(state);
+  const orch = createOrchestrator(store, noopLog, deps);
+  orch.claimTick();
+  assert.equal(state.spawned.length, 1);
+  assert.equal(store.globalInflightCount(), 1, '已有 1 个在途 started run');
+  // 再来一轮：全局在途已=1=cap → 不再领
+  orch.claimTick();
+  assert.equal(state.spawned.length, 1, '全局在途已达上限 → 整轮不领');
+  assert.ok(store.listTasks(p1).length >= 0);
+  store.close();
+});
+
 test('并发闸用 inflight：1 个 executing + 1 个 planner 占满 concurrency=2', () => {
   const { store, projectId } = setup('auto-approved', 2);
   const e = store.createTask({ projectId, title: 'easy', complexity: 'easy' });    // → ready