Complete Kitty keyboard phases and stable fallback key metadata

Normalized profile

What this task asks for

Add full Kitty keyboard phase handling and stable fallback key metadata for keys and shortcuts. Extend Keys public API with exact stored fields phase, modifiers, base_key, shifted_key, and base_layout_key. Phase is "press", "repeat", or "release" defaulting to "press", and modifiers is a sorted tuple. Also expose convenience properties is_press, is_repeat, is_release, shift, alt, ctrl, super, hyper, and meta. Preserve printable semantics: shift-only printable Kitty events must preserve the shifted character and metadata, so character stays "A", modifiers reports ("shift",), and base_key stays "a". Non-shift modified printable shortcuts must keep names like "alt+shift+a" with character=None, associated-text-only key-code 0 uses its text as both key and character, and alternate metadata uses Textual names like shifted_key="plus" and alias ctrl+plus. Add examples/kitty_keyboard_protocol.py with KittyKeyboardProtocolApp, RichLog id events, guarded entrypoint, and log lines containing literal phase=<phase> and character=<repr(character)>.