Persist mouse-gesture binding selection, add numeric chooser and wheel-gate

[multiplex55]

Motivation

• Remember and restore the last-selected binding for a gesture (label+tokens) so repeated gestures default to the user’s last choice.
• Improve multi-binding UX by showing a numbered chooser in the hint overlay and allowing numeric keyboard selection as well as gated wheel cycling.

Description

• Added a lightweight JSON state store (mouse_gestures_state.json) and helper functions load_selection_state / save_selection_state to persist last-selected binding index per gesture (keyed by label::tokens).
• Extended MouseGestureConfig with wheel_cycle_gate and new WheelCycleGate enum, wired through plugin settings (MouseGestureSettings) and the GUI settings dialog (mouse_gesture_settings_dialog.rs).
• Updated service.rs to initialize selected_binding_idx from stored state when an exact candidate appears, and to save selection on SelectBinding / wheel-cycling changes.
• Reworked hint rendering in format_hint_text to output a numbered binding chooser (e.g. 1) Action A, 2) Action B) and to include updated hint text describing the wheel gate and numeric selection.
• Extended HookEvent to include CycleNext, CyclePrev, and SelectBinding(usize) and updated hook logic to map mouse wheel to cycle events and 1-9 key presses to SelectBinding when a gesture is active; added platform gate logic so wheel cycling can be gated behind deadzone or Shift+Wheel on Windows.
• Added wheel_gate state to the Windows HookDispatch and appropriate logic in mouse_hook_proc / keyboard_hook_proc to enforce the gate and forward cycle/select events.
• Added unit tests in tests/mouse_gestures_service.rs covering selection persistence across gesture sessions and numeric selection updating the hint overlay, and adjusted an existing hint text assertion to the new format.

Testing

• Ran cargo fmt successfully to format changes.
• Attempted cargo test mouse_gestures_service, but the test run failed during build due to an external system dependency (missing system alsa / alsa.pc) required by alsa-sys; the added tests are present but could not be executed in this environment because of that missing native dependency.

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Codex Task