Add named keyboard binding modes (#32)

Add named keyboard shortcut maps with an Escape exit and a panel indicator. Keep press/release ownership across transitions, validate remapped Escape keys, and cancel stale repeats and focus previews.

Give the indicator ownership of the panel while a mode is active. Close popovers, collapse Morph, and keep Live Activities data current without resizing the hidden panel. Document configuration and transition behavior.

Validation: 1,519 workspace Rust tests passed; 70 Python tests passed. Workspace build, formatting, Clippy, and Settings configuration validation passed. Opt-in native desktop checks were not rerun because Weston is absent.

Related: #5.

compositor/src/backends/direct.rs

@@ -376,6 +376,7 @@ pub fn init(event_loop: &mut EventLoop<Ferese>, state: &mut Ferese) -> Result<()
         .handle()
         .insert_source(notifier, move |event, _, state| match event {
             SessionEvent::PauseSession => {
+                state.set_binding_mode("default");
                 let handle = state.loop_handle.clone();
                 if let Some(backend) = state.direct_backend.as_mut() {
                     backend.active = false;