Merge master into subagent usage branch

# Conflicts:
#	.agents/notes/implemented/feature/2026-07-27-web-subagent-conversations.i18n.yaml
#	.agents/notes/implemented/feature/2026-07-27-web-subagent-conversations.md
#	.agents/notes/implemented/feature/2026-07-27-web-subagent-conversations.zh.md
#	apps/web/tests/snapshots/subagent-conversation/tree.expected.md
#	apps/web/tests/subagent-conversation.e2e.ts
#	packages/client/ui-subagent/src/client/SubagentCatalogAction.tsx

packages/client/runtime/tests/manager.spec.ts

@@ -529,6 +529,149 @@ describe('subagent catalogs', () => {
       { kind: 'child', id: S2, activity: 'inactive' },
     ])
   })
+
+  it('coalesces overlapping catalog reads without scheduling a trailing pull', async () => {
+    const api = new FakeApiClient()
+    const root = 'fk-root' as SessionId
+    const first = deferred<Awaited<ReturnType<FakeApiClient['onSubagentList']>>>()
+    api.onSubagentList = () => first.promise
+    const manager = new SessionManager(api)
+
+    const refresh = manager.refreshSubagents(root)
+    expect(manager.refreshSubagents(root)).toBe(refresh)
+    api.onSubagentList = () => Promise.resolve(ok({ entries: [], parentAvailable: true }))
+    first.resolve(ok({ entries: [], parentAvailable: true }))
+    await refresh
+
+    expect(api.callsOf('subagent.list')).toHaveLength(1)
+  })
+
+  it('runs one trailing catalog refresh for a membership change coalesced into an in-flight pull', async () => {
+    vi.useFakeTimers()
+    try {
+      const api = new FakeApiClient()
+      const root = 'fk-root' as SessionId
+      const first = deferred<Awaited<ReturnType<FakeApiClient['onSubagentList']>>>()
+      const second = deferred<Awaited<ReturnType<FakeApiClient['onSubagentList']>>>()
+      api.onSubagentList = () => first.promise
+      const manager = new SessionManager(api, root)
+      const refresh = manager.refreshSubagents(root)
+
+      // A membership frame arrives while the pull is in flight; the debounced
+      // refresh it schedules fires 50ms later and is coalesced into the pull —
+      // which was requested before the new child existed. The stale mark must
+      // queue one trailing pull carrying the change.
+      manager.handleHostEnvelope({
+        rpcId: 'child-added' as never,
+        payload: {
+          type: 'host/session-added', sessionId: S2, parentSessionId: root, blank: false,
+        },
+      })
+      await vi.advanceTimersByTimeAsync(50)
+      api.onSubagentList = () => second.promise
+      first.resolve(ok({
+        entries: [{
+          kind: 'child', id: S1, mode: 'continuable', label: 'older',
+          activity: 'inactive', hasChildren: false,
+        }] as never[],
+        parentAvailable: true,
+      }))
+      await refresh
+      // The trailing pull is already in flight (kicked synchronously in finally).
+      second.resolve(ok({
+        entries: [
+          {
+            kind: 'child', id: S1, mode: 'continuable', label: 'older',
+            activity: 'inactive', hasChildren: false,
+          },
+          {
+            kind: 'child', id: S2, mode: 'continuable', label: 'new child',
+            activity: 'inactive', hasChildren: false,
+          },
+        ] as never[],
+        parentAvailable: true,
+      }))
+      await second.promise
+
+      expect(api.callsOf('subagent.list')).toHaveLength(2)
+      expect(manager.getListSnapshot().subagentsByParent[root]?.entries).toMatchObject([
+        { kind: 'child', id: S1, label: 'older' },
+        { kind: 'child', id: S2, label: 'new child' },
+      ])
+    } finally {
+      vi.useRealTimers()
+    }
+  })
+
+  it('keeps removal invalidation across a stale success and failed trailing pull', async () => {
+    const api = new FakeApiClient()
+    const root = 'fk-root' as SessionId
+    const child = () => ({
+      kind: 'child' as const, id: S2, mode: 'continuable' as const, label: 'worker',
+      activity: 'inactive' as const, hasChildren: false,
+    })
+    const first = deferred<Awaited<ReturnType<FakeApiClient['onSubagentList']>>>()
+    api.onSubagentList = () => first.promise
+    const manager = new SessionManager(api)
+    const refresh = manager.refreshSubagents(root)
+    first.resolve(ok({ entries: [child()] as never[], parentAvailable: true }))
+    await refresh
+    manager.selectSubagent({ parentSessionId: root, childSessionId: S2, mode: 'continuable' })
+
+    // The removal lands while a second pull is in flight: the invalidation
+    // must survive the pre-removal ok response, so one trailing pull runs.
+    const mid = deferred<Awaited<ReturnType<FakeApiClient['onSubagentList']>>>()
+    api.onSubagentList = () => mid.promise
+    const midRefresh = manager.refreshSubagents(root)
+    manager.handleHostEnvelope({
+      rpcId: 'parent-removed-mid-pull' as never,
+      payload: { type: 'host/session-removed', sessionId: root },
+    })
+    const trailing = deferred<Awaited<ReturnType<FakeApiClient['onSubagentList']>>>()
+    api.onSubagentList = () => trailing.promise
+    mid.resolve(ok({ entries: [child()] as never[], parentAvailable: true }))
+    await midRefresh
+    expect(manager.getListSnapshot().subagentsByParent[root]?.parentAvailable).toBe(false)
+    expect(manager.get(S2).getSnapshot().subagent).toMatchObject({ parentAvailable: false })
+
+    trailing.resolve(err({ code: 'internal', message: 'trailing pull failed', details: {} }))
+    await vi.waitFor(() => {
+      expect(manager.getListSnapshot().subagentsByParent[root]).toMatchObject({
+        state: 'error',
+        parentAvailable: false,
+      })
+    })
+
+    const rootCalls = api.callsOf('subagent.list')
+      .filter(call => (call as { parentSessionId: SessionId }).parentSessionId === root)
+    expect(rootCalls).toHaveLength(3)
+    expect(manager.getListSnapshot().subagentsByParent[root]?.parentAvailable).toBe(false)
+    expect(manager.get(S2).getSnapshot().subagent).toMatchObject({ parentAvailable: false })
+  })
+
+  it('invalidates catalog availability when the owning parent is removed', async () => {
+    const api = new FakeApiClient()
+    const root = 'fk-root' as SessionId
+    api.onSubagentList = () => Promise.resolve(ok({
+      entries: [{
+        kind: 'child', id: S2, mode: 'continuable', label: 'worker',
+        activity: 'inactive', hasChildren: false,
+      }] as never[],
+      parentAvailable: true,
+    }))
+    const manager = new SessionManager(api)
+    await manager.refreshSubagents(root)
+    manager.selectSubagent({ parentSessionId: root, childSessionId: S2, mode: 'continuable' })
+    expect(manager.get(S2).getSnapshot().subagent).toMatchObject({ parentAvailable: true })
+
+    manager.handleHostEnvelope({
+      rpcId: 'parent-removed' as never,
+      payload: { type: 'host/session-removed', sessionId: root },
+    })
+
+    expect(manager.getListSnapshot().subagentsByParent[root]?.parentAvailable).toBe(false)
+    expect(manager.get(S2).getSnapshot().subagent).toMatchObject({ parentAvailable: false })
+  })
 })
 
 describe('remaining branches', () => {