fix(app): keep dictation running when agent tab loses focus

Previously, dictation was cancelled the moment the user switched away
from the active agent tab, losing any in-progress recording. Drop the
auto-stop-on-blur behavior so users can start dictating, switch tabs,
and come back to finalize.

packages/app/src/hooks/use-dictation.shared.ts

@@ -8,7 +8,6 @@ export interface UseDictationOptions {
   onPermanentFailure?: (error: Error, context: { requestId: string }) => void;
   canStart?: () => boolean;
   canConfirm?: () => boolean;
-  autoStopWhenHidden?: { isVisible: boolean };
   enableDuration?: boolean;
 }