dom: fix macOS text input navigation and clipboard keybindings

[GoCoder7]

Fixes #894.

Summary

This PR addresses several macOS keyboard navigation, shortcut, and clipboard issues in blitz-dom text inputs by adopting the pattern used in VS Code and Zed's editor architecture:

1. Prevent 2-character jumping on plain arrow keys:

   • On macOS, winit emits both AppleStandardKeyBinding and raw KeyPress.
   • In apply_keypress_event, plain/Option navigation keys are left to AppleStandardKeyBinding so that AppKit can handle them natively (moveLeft:, moveWordLeft:) without duplicate execution.

2. Support macOS Cmd + Arrow navigation and Cmd + Backspace:

   • AppKit's interpretKeyEvents: treats Cmd keys as application commands and does not emit standard text selectors for them.
   • Handled Cmd + Left/Right (move to line start/end), Cmd + Up/Down (move to document start/end), their Shift selection variants, and Cmd + Backspace (delete to line start) directly in apply_keypress_event.

3. Support clipboard operations in AppleStandardKeyBinding:

   • Added match arms for "copy:", "cut:", and "paste:" in apply_apple_standard_keybinding.
   • Prevented spurious Input events when performing copy.

4. Fix selector typo:

   • Fixed typo in "moveToEndOfDocumentAndModifySelection:" calling driver.move_to_text_end() instead of driver.select_to_text_end().

5. Physical key (Code) mapping for action shortcuts across non-Latin keyboard layouts:

   • Previously, shortcuts were matched only against Key::Character("a" | "c" | "v" | "x"). On non-Latin keyboard layouts (e.g. Korean 2-Set where physical KeyC generates ㅊ), shortcuts failed completely.
   • Introduced action_key helper in util.rs to normalize action keystrokes (Cmd on macOS, Ctrl on others) by prioritizing physical key codes (Code::KeyA, KeyC, KeyV, KeyX, KeyZ) with character fallback.
   • Refactored shortcut dispatching in both TextInputData::apply_keypress_event and handle_key_or_input_event using a concise match action_key(&event) pattern.

Testing

• cargo fmt --all --check: Passed.
• cargo clippy -p blitz-dom -- -D warnings: Passed (0 warnings).
• cargo test -p blitz-dom: 56/56 unit tests passed.
• Tested manually on macOS with wgpu_texture text input across all combinations:
  • Plain arrows (1 character)
  • Option + Arrow (word jump)
  • Cmd + Arrow (line start/end, document start/end)
  • Shift modifier combinations for all the above (selection)
  • Cmd + Backspace (delete to line start)
  • Cmd + C / Cmd + V / Cmd + X / Cmd + A on both English and non-Latin (Korean) layouts

WPT results

No changes in test results compared to main.

_{Generated by the WPT workflow.}