[FacuM]

Stacked on #1; retarget to main after #1 merges.

Summary

Adds wlroots-based backends to the Linux host: Sway and Hyprland. Each one creates a virtual output over the compositor's IPC, captures it directly over Wayland (no portal), and maps the uinput input devices to that output. The PipeWire path is unchanged.

Changes

• Sway (sway.rs): i3-ipc client over $SWAYSOCK. Creates a HEADLESS-n output, sets its mode with mode --custom, unplugs it on exit, and maps each input device with map_to_output.
• Hyprland (hyprland.rs): socket IPC. Creates ezdisplay-N with output create headless, sets the mode with keyword monitor, removes it with output remove, and maps devices with keyword device[...]:output.
• Direct Wayland capture (wl_capture.rs): uses ext-image-copy-capture-v1 with an output capture source and a pointer cursor session, so the tablet's local cursor works. Falls back to wlr-screencopy with the cursor painted into the frame. Only wl_shm buffers are used; DMA-BUF is not yet supported.
• Override: EZD_WL_CAPTURE=ext|wlr|auto selects the capture protocol.
• Source selection (source.rs): the capture source is now Capture::{Pw, Wl}. The PipeWire path is unchanged.
• Input mapping: absolute pointers are mapped per device on wlroots. The workspace Mapper is not used there.
• Diagnostics (diag.rs): reports the compositor, its version, and the capture protocols it advertises.
• Tests and tooling: fixtures for Sway's get_outputs and get_version, unit tests for the Hyprland IPC parsing, tools/wlroots-headless-test.sh (runs headless Sway in Docker when EZD_WLROOTS_TEST=1), and docs updates in docs/architecture.md, docs/input.md, README.md and packaging/linux/.

Scope notes

• Hyprland has not been run live. It fails to start headless in a container, so its coverage is unit tests with fixtures.
• Not tested on real Sway or Hyprland sessions with a GPU.
• DMA-BUF capture and 10-bit capture are not covered.
• Live uinput mapping on wlroots compositors is not covered.

Verification

• cargo fmt --check, cargo clippy -- -D warnings and cargo test --workspace pass.
• Headless Sway 1.12 in Docker (tools/wlroots-headless-test.sh, EZD_WLROOTS_TEST=1):
  • The output is created at 1280x720@60.
  • Frames are captured with real damage and encoded with libx264.
  • 15–16 cursor updates arrive on ext-image-copy-capture.
  • The cursor is embedded on wlr-screencopy.
  • The output is unplugged afterwards.
  • Sway accepts map_to_output for all devices.
• Real KDE Plasma session re-checked end to end with ezd-fake-client: no regression. Virtual output is 1920x1080, and touch and pen are mapped.