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.

nexusos_cli/tui_app.py

@@ -27,13 +27,14 @@ _APPROVAL_TIMEOUT = httpx.Timeout(10.0, connect=5.0)
 def _require_textual():
     try:
         from textual.app import App
+        from textual.binding import Binding
         from textual.widgets import Footer, Header, Input, RichLog, Static
     except ImportError as e:  # pragma: no cover - optional extra
         raise ImportError(
             "The interactive TUI needs the 'tui' extra — "
             "pip install 'nexusos-ai[tui]' (or: pip install textual)."
         ) from e
-    return App, Footer, Header, Input, RichLog, Static
+    return App, Binding, Footer, Header, Input, RichLog, Static
 
 
 def _escape(text: str) -> str:
@@ -154,7 +155,7 @@ class NexusTUI:
 
     @staticmethod
     def build_app(*, api_url: str | None = None):
-        App, Footer, Header, Input, RichLog, Static = _require_textual()
+        App, Binding, Footer, Header, Input, RichLog, Static = _require_textual()
         base = (api_url or settings.api_url).rstrip("/")
 
         class AppImpl(App):
@@ -187,8 +188,8 @@ class NexusTUI:
             #prompt { dock: bottom; }
             """
             BINDINGS = [
-                ("ctrl+c", "interrupt", "Interrupt"),
-                ("ctrl+d", "quit", "Quit"),
+                Binding("ctrl+c", "interrupt", "Interrupt", priority=True),
+                Binding("ctrl+d", "quit", "Quit", priority=True),
             ]
 
             def __init__(self):