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.

docs/ipc.md

@@ -1,5 +1,9 @@
 # feresectl and IPC events
 
+`feresectl keybindings` lists the active binding mode's shortcuts. Outside a
+mode it lists the configured default shortcuts. Escape is always available to
+leave a mode; see [Binding modes](configuration.md#binding-modes).
+
 `feresectl` controls a running Ferese session. Run `feresectl --help` for commands
 and `feresectl COMMAND --help` for arguments.