fix(pty): fence delayed signal prompts

packages/pty/pty-local/tests/session.spec.ts

@@ -591,6 +591,35 @@ describe('LocalPtySession readiness and output', () => {
     expect(await operation.done).toMatchObject({ waitReason: 'stdin_read' })
   })
 
+  it('does not attribute a post-echo prompt from an inferred prior send to its successor', async () => {
+    vi.useFakeTimers()
+    const terminal = new FakeTerminal()
+    const session = new LocalPtySession(terminal, config({ idleSilenceMs: 50, timeoutMs: 200 }))
+    await initialize(session, terminal)
+
+    const interrupted = session.startSend({ text: 'sleep', submit: true })
+    await Promise.resolve()
+    await Promise.resolve()
+    await session.signal('SIGINT')
+    await vi.advanceTimersByTimeAsync(50)
+    expect((await interrupted.done).waitReason).toBe('inferred_idle')
+
+    const successor = session.startSend({ text: "printf 'PID=%s\\n' \"$!\"", submit: true })
+    let settled = false
+    void successor.done.then(() => { settled = true })
+    await Promise.resolve()
+    await Promise.resolve()
+    terminal.emitData('printf \'PID=%s\\n\' "$!"\r\n\x1b]133;D;130\x07dsh> ')
+    await vi.advanceTimersByTimeAsync(10)
+    expect(settled).toBe(false)
+
+    terminal.emitData('PID=123\r\n\x1b]133;D;0\x07dsh> ')
+    await vi.advanceTimersByTimeAsync(10)
+    const result = await successor.done
+    expect(result.waitReason).toBe('stdin_read')
+    expect(result.viewport).toContain('PID=123')
+  })
+
   it('retains a prompt marker until the startup shell regains the foreground group', async () => {
     vi.useFakeTimers()
     const terminal = new FakeTerminal()