fix: wrap session resume in @work to resolve NoActiveWorker crash

push_screen_wait requires a worker context, but on_mount is a plain
lifecycle callback. Extract session resume logic into a @work-decorated
method so the modal can be awaited without triggering NoActiveWorker.

app/ui/app.py

@@ -11,6 +11,7 @@ from rich.text import Text
 from textual.app import App, ComposeResult
 from textual.binding import Binding
 from textual.widgets import Header, RichLog
+from textual import work
 
 from app.agent.context import SessionContext
 from app.agent.loop import AgentLoop
@@ -106,7 +107,12 @@ class SneakyCodeApp(App):
 
         self._permissions.set_prompt_callback(permission_prompt)
 
-        # Offer session resume if configured
+        # Offer session resume if configured (must run in a worker for push_screen_wait)
+        self._offer_session_resume()
+
+    @work
+    async def _offer_session_resume(self) -> None:
+        """Offer to resume a previous session, running in a worker for modal support."""
         if self._session_mgr and self._config.session.offer_resume:
             saved = self._session_mgr.load_latest()
             if saved:
@@ -118,7 +124,6 @@ class SneakyCodeApp(App):
                     log.write(Text("Session restored", style="bold green"))
                 else:
                     log.write(Text("Starting fresh session", style="cyan"))
-
         self.query_one(HistoryInput).focus()
 
     async def on_input_submitted(self, event: Input.Submitted) -> None: