fix(tasks): 逐节点折叠按钮在聚合规则下失效（手动折叠不再共用自动折叠的守卫）

用户反馈「怎么折叠和怎么自动合并功能没了？我点击没反应」。

根因是折叠入口把两个触发条件塞进了同一组守卫：

    if ((folded || foldedIds?.has(child.id)) && isLeaf && !child.current
        && child.team === undefined && (done || error))

`child.team === undefined` 是给**页面级自动聚合**准备的（teammate 是真实可续接
的工作者，不该被自动扫走），但它同样卡住了 `foldedIds` 这条**手动**路径。而卡片小条
的折叠 chevron 是按「已结算」画出来的——于是出现「按钮画出来了，点了没反应」这种
最差的失效形态：既没有折叠，也没有任何反馈。

改为按触发源分别守卫（`isAutoFoldable` = leaf + 非成员；`nodeFoldable` = 已结算 +
非当前会话），手动折叠只需后者；workflow run 成员两个触发都走 `nodeFoldable`。

测试：新增 4 例——手动折叠把「出错」的成员收进聚合、自动规则不动它、
运行中的成员即使用手动折叠也不被收起；pnpm test 1279 passed / 9 skipped，
typecheck / lint 通过。

(cherry picked from commit 3a47ddafe3c2d57f8997dc97f0118eb0530b114a)

tests/tasks-model.spec.ts

@@ -155,6 +155,46 @@ describe('buildTasksModel', () => {
     expect(agents(model).find(node => node.id === 'w')?.state).toBe('running')
   })
 
+  it('folds a settled team member when the READER folds it by hand', () => {
+    // The card's chevron is drawn whenever a node is settled, and a teammate
+    // can settle as 出错 (a failed roster row). Auto-fold keeps team members
+    // out of the aggregate — a roster row is a real, resumable worker, not a
+    // settled subagent to sweep away — but a manual fold is the reader's
+    // explicit request for THAT node and must not be silently dropped.
+    const model = buildTasksModel(input({
+      catalogs: { root: catalog([child('mate'), child('sub')]), sub: catalog([]) },
+      byId: { root: summary('root'), mate: summary('mate'), sub: summary('sub') },
+      teamMembers: [member({ id: 'mate', phase: 'failed', status: 'failed' })],
+      folded: false,
+      foldedIds: new Set(['mate', 'sub']),
+    }))
+    expect(model.map(node => node.id)).toEqual(['root', 'fold:root'])
+    expect(model.find(node => node.kind === 'fold')).toMatchObject({
+      count: 2, memberIds: ['mate', 'sub'],
+    })
+  })
+
+  it('leaves a failed teammate alone under the AUTO rule (only a manual fold takes it)', () => {
+    const model = buildTasksModel(input({
+      catalogs: { root: catalog([child('mate'), child('sub')]), sub: catalog([]) },
+      byId: { root: summary('root'), mate: summary('mate'), sub: summary('sub') },
+      teamMembers: [member({ id: 'mate', phase: 'failed', status: 'failed' })],
+      folded: true,
+    }))
+    expect(model.map(node => node.id)).toEqual(['root', 'mate', 'fold:root'])
+  })
+
+  it('never folds a RUNNING team member, even when the reader clicks its chevron', () => {
+    const model = buildTasksModel(input({
+      catalogs: { root: catalog([child('mate')]) },
+      byId: { root: summary('root'), mate: summary('mate') },
+      teamMembers: [member({ id: 'mate', phase: 'active', status: 'running' })],
+      folded: false,
+      foldedIds: new Set(['mate']),
+    }))
+    expect(model.map(node => node.id)).toEqual(['root', 'mate'])
+  })
+
   it('folds settled leaves per parent and keeps running/teammate/current rows', () => {
     const model = buildTasksModel(input({
       catalogs: {