feat: add Ctrl+O activity panel toggle, fix terminal 997;1n garbage on exit

Wire up the activity_toggle keybind (Ctrl+O) to show/hide the activity
panel via new activityVisible store state. Fix terminal garbage text on
exit by draining stdin after renderer teardown to consume pending
DECRQM mode 997 responses before they echo in the shell.

README.md

@@ -97,6 +97,7 @@ Full-screen terminal interface with real-time streaming responses.
 - `/` - Open command menu (works anywhere in input)
 - `Ctrl+M` - Toggle interaction mode
 - `Ctrl+T` - Toggle todo panel
+- `Ctrl+O` - Toggle activity panel
 - `Shift+Up/Down` - Scroll log panel
 - `Ctrl+C` (twice) - Exit
 
@@ -465,7 +466,9 @@ bun run lint
 ## Recent Changes (v0.4.2)
 
 - **Pink Purple Theme**: New built-in color theme
+- **Activity Panel Toggle**: `Ctrl+O` to show/hide the activity panel
 - **Image Paste Fix**: Fixed race condition where pasted images were silently dropped
+- **Terminal Exit Fix**: Fixed `997;1n` garbage text appearing on exit
 - **@ and / Anywhere**: File picker and command menu now work at any cursor position
 - **Plan Approval Gate**: User confirmation before agent executes plans
 - **Execution Control**: Pause, resume, and abort agent execution