fix(hotkey): rearm raw input sink on mid-run hotkey change + delayed focus re-assertion

Two fixes:

1. Start menu leak on mid-run Win hotkey change: reregister_hotkey_listener
   now calls rearm_raw_input_sink() after creating new HotkeyListener.
   Without this, switching from non-Win to Win mid-run left the raw input
   sink without RIDEV_NOHOTKEYS, so bare Win presses opened Start.

2. Win key overlay focus: added FocusReassert UiCommand — a 250ms delayed
   re-assertion after Painted that calls force_foreground + focus_input.
   Explorer re-asserts foreground ~100-200ms after Win key-down reaches the
   OS; the second attempt after 250ms catches Explorer once it has settled.