feat: input-method-v1

[WantenMN]

Description

This PR introduces protocol handling for the unstable v1 IME stack:

• zwp_input_method_v1
• zwp_text_input_manager_v1 / zwp_text_input_v1
• zwp_input_panel_v1 / zwp_input_panel_surface_v1

It adds a new wayland::input_method_v1 module and exports it from wayland::mod.

What is included:

• New manager state: InputMethodV1ManagerState
  • Creates and exposes globals for input-method-v1, text-input-v1 and input-panel-v1.
  • Supports client filtering through the same global filter pattern used in Smithay modules.
• New compositor callback trait: InputMethodV1Handler
  • new_popup
  • dismiss_popup
  • popup_repositioned
  • parent_geometry
• Popup lifecycle support for zwp_input_panel_surface_v1
  • Tracks popup parent surface and logical geometry.
  • Updates popup placement from text-input cursor rectangle changes.
• Text-input <-> input-method bridging
  • Activation/deactivation wiring.
  • Forwarding of surrounding text, content type, preferred language, state commits and actions.
  • Forwarding of commit/preedit/delete/cursor/modifier/language/direction events from IME context back to active text input.
• Keyboard integration
  • Supports grab_keyboard on IME context.
  • Sends keymap/repeat info/modifiers to IME keyboard resource.
  • Forwards key/modifier events to focused keyboards where appropriate.
• Delegate macro for downstream compositors:
  • delegate_input_method_manager_v1!

API/docs polish:

• Added rustdoc comments for the public API exposed by wayland::input_method_v1.
• Kept behavior unchanged while improving maintainability/readability of the public surface.

Validation:

• cargo fmt --all
• cargo check -q
• cargo test -q --lib (72 passed)

Related issue:

• Closes Would a input-method-v1 implementation be accepted? #1914

Checklist

[ x ] I agree to smithay's Developer Certificate of Origin.