fix(tui): prioritize interrupt and quit keys

Declare Ctrl+C and Ctrl+D as priority Textual bindings so the focused prompt cannot consume them. Drive exit and silent-stream cancellation regressions through Pilot key events instead of calling action handlers directly.

tests/test_tui.py

@@ -123,6 +123,23 @@ def test_stream_error_remains_visible_after_finish():
     asyncio.run(_run())
 
 
+@pytest.mark.parametrize("key", ["ctrl+c", "ctrl+d"])
+def test_priority_exit_bindings_reach_app_while_prompt_is_focused(key):
+    pytest.importorskip("textual")
+    from nexusos_cli.tui_app import NexusTUI
+
+    app = NexusTUI.build_app(api_url="http://127.0.0.1:9")
+
+    async def _run():
+        async with app.run_test() as pilot:
+            assert app.is_running
+            await pilot.press(key)
+            await pilot.pause()
+            assert not app.is_running
+
+    asyncio.run(_run())
+
+
 def test_tool_request_is_denied_with_stream_token():
     _ApprovalClient.calls.clear()
     names = _deny_tool_request(
@@ -262,13 +279,14 @@ def test_interrupt_cancels_silent_stream_and_accepts_next_message(monkeypatch):
         pytest.fail("stream did not become idle within one second")
 
     async def _run():
-        async with app.run_test():
+        async with app.run_test() as pilot:
             app._start_chat("first")
             assert await asyncio.to_thread(first_stream_started.wait, 2)
-            app.action_interrupt()
+            await pilot.press("ctrl+c")
             await _wait_until_idle()
 
             log = app.query_one("#log")
+            assert any("interrupt requested" in line.text for line in log.lines)
             assert not any("ReadTimeout" in line.text for line in log.lines)
 
             app._start_chat("second")