Implement native InputCapture with private EIS receiver transport

Add consent, zones and outside-edge barriers, connection-scoped leases, bounded input queues and keyboard/pointer forwarding. Restore local input on release, locking, topology or keymap changes, receiver loss and emergency escape. Preserve held-key state and distinguish finger stops from absent scroll axes.

Validation: independent review cleared; 5 native InputCapture unit tests; 32 portal tests; official D-Bus contract checks on a private bus; real installed libei receiver interoperability test. Live physical barrier and consent interaction remain to be checked in a desktop session.

compositor/src/handlers/layer_shell.rs

@@ -108,6 +108,7 @@ pub fn handle_commit(state: &mut Ferese, surface: &WlSurface) {
 
     let policy = layer.cached_state();
     if !state.session_lock.active
+        && !state.input_capture.captures(1)
         && policy.keyboard_interactivity == KeyboardInteractivity::Exclusive
         && matches!(policy.layer, Layer::Top | Layer::Overlay)
     {