fix: show scan error as TUI toast before exit

Scan errors were stored in _scan_error and re-raised only after the
user closed the TUI, making the app appear stuck while producing a
confusing post-exit traceback.

Extract _notify_scan_error and call it from all three error branches
in _start_scan_thread so a persistent Textual toast is shown
immediately when the scan thread fails.

strix/interface/tui/app.py

@@ -1378,12 +1378,15 @@ class StrixTUIApp(App):  # type: ignore[misc]
                 except (ConnectionError, TimeoutError) as e:
                     logging.exception("Network error during scan")
                     self._scan_error = e
+                    self._notify_scan_error(e)
                 except RuntimeError as e:
                     logging.exception("Runtime error during scan")
                     self._scan_error = e
+                    self._notify_scan_error(e)
                 except Exception as e:
                     logging.exception("Unexpected error during scan")
                     self._scan_error = e
+                    self._notify_scan_error(e)
                 finally:
                     with contextlib.suppress(Exception):
                         loop.run_until_complete(
@@ -1399,6 +1402,16 @@ class StrixTUIApp(App):  # type: ignore[misc]
         self._scan_thread = threading.Thread(target=scan_target, daemon=True)
         self._scan_thread.start()
 
+    def _notify_scan_error(self, exc: Exception) -> None:
+        """Dispatch a persistent error toast from any thread."""
+        with contextlib.suppress(Exception):
+            self.call_from_thread(
+                self.notify,
+                f"Scan failed: {type(exc).__name__}: {exc}",
+                severity="error",
+                timeout=0,
+            )
+
     def _capture_sdk_event(self, agent_id: str, event: Any) -> None:
         try:
             self.call_from_thread(self._record_sdk_event, agent_id, event)

tests/interface/tui/test_app.py

@@ -0,0 +1,47 @@
+"""Tests for StrixTUIApp._notify_scan_error — Fix 2: in-TUI error display."""
+
+from __future__ import annotations
+
+from unittest.mock import MagicMock
+
+from strix.interface.tui.app import StrixTUIApp
+
+
+def _mock_app() -> MagicMock:
+    return MagicMock(spec=StrixTUIApp)
+
+
+def test_notify_scan_error_dispatches_toast() -> None:
+    """_notify_scan_error must call notify via call_from_thread with error text."""
+    app = _mock_app()
+    exc = RuntimeError("something went wrong")
+
+    StrixTUIApp._notify_scan_error(app, exc)
+
+    app.call_from_thread.assert_called_once_with(
+        app.notify,
+        "Scan failed: RuntimeError: something went wrong",
+        severity="error",
+        timeout=0,
+    )
+
+
+def test_notify_scan_error_suppresses_call_from_thread_failure() -> None:
+    """If call_from_thread itself raises, the exception must be swallowed."""
+    app = _mock_app()
+    app.call_from_thread.side_effect = RuntimeError("TUI not ready")
+
+    # Must not propagate the exception.
+    StrixTUIApp._notify_scan_error(app, ValueError("boom"))
+
+
+def test_notify_scan_error_formats_exception_type() -> None:
+    """Toast text must include the exception's class name and message."""
+    app = _mock_app()
+    exc = ConnectionError("host unreachable")
+
+    StrixTUIApp._notify_scan_error(app, exc)
+
+    args = app.call_from_thread.call_args.args
+    assert "ConnectionError" in args[1]
+    assert "host unreachable" in args[1]