fix(web): address review on the turn-tail actions gate

Correct the Agent Note's consequence: a running turn withholds the footer
below its own trigger bubble, while every earlier completed turn keeps its
seat — which the package test already asserts.

Give the running-phase barrier an explicit budget: it is armed before the
park and awaited after the stop click, so the 30s replay default left no
headroom for the marker poll, the UI polls, and two aria captures.

Number the running-turn test's boundary seqs like the log does, with each
turn/end strictly after its own nodes.

packages/client/ui-conversation/tests/chat-view.spec.tsx

@@ -537,18 +537,20 @@ describe('ChatView', () => {
       nodes: [
         user(1, 'first'),
         assistant(2, 'previous answer', 1),
-        user(3, 'second'),
-        assistant(4, 'mid-turn text', 2),
+        user(4, 'second'),
+        assistant(5, 'mid-turn text', 2),
       ],
-      turnEnds: new Map([[1, 2]]),
+      // Boundary seqs follow the log: a turn/end is strictly after its own nodes.
+      turnEnds: new Map([[1, 3]]),
     })
     const view = render(<h.ChatView {...h.props} />)
-    // 2 user + the settled turn-1 tail; turn 2's narration stays chrome-free
-    // while its tool runs, so the footer never appears and then moves.
+    // 2 user + the settled turn-1 tail, which keeps its seat while a later
+    // turn runs; turn 2's narration stays chrome-free while its tool runs, so
+    // the footer never appears and then moves.
     expect(view.getAllByRole('button', { name: '复制' })).toHaveLength(3)
     expect(view.getByText('mid-turn text')).toBeTruthy()
     // turn/end lands: the same node becomes the settled answer and takes the seat.
-    act(() => { h.set({ running: false, runningCalls: [], turnEnds: new Map([[1, 2], [2, 5]]) }) })
+    act(() => { h.set({ running: false, runningCalls: [], turnEnds: new Map([[1, 3], [2, 6]]) }) })
     expect(view.getAllByRole('button', { name: '复制' })).toHaveLength(4)
   })