config/wayland.toml: fix misleading kwin_pid→compositor_pid

The Wayland compositor service currently launches redbear-compositor,
not kwin_wayland. Renamed kwin_pid→compositor_pid and updated the
error message from 'kwin_wayland failed' to 'Wayland compositor failed'.

Added comment documenting that redbear-compositor is the bootstrap
compositor until KWin completes its build. The transition path is
documented: replace 'redbear-compositor --drm' with 'kwin_wayland --drm'
when KWin is runtime-ready.

config/wayland.toml

@@ -211,7 +211,7 @@ wait_for_wayland_socket() {
         if [ -e "$socket_path" ]; then
             return 0
         fi
-        if ! kill -0 "$kwin_pid" 2>/scheme/null; then
+        if ! kill -0 "$compositor_pid" 2>/scheme/null; then
             return 1
         fi
         attempts=$((attempts + 1))
@@ -245,11 +245,14 @@ if [ -z "${KWIN_DRM_DEVICES:-}" ] && [ -e /scheme/drm/card0 ]; then
     export KWIN_DRM_DEVICES=/scheme/drm/card0
 fi
 
+# Bootstrap compositor: redbear-compositor provides a bounded Wayland
+# surface (DRM/KMS + core protocols) until KWin completes its build.
+# When KWin is ready, replace with: kwin_wayland --drm &
 redbear-compositor --drm &
-kwin_pid=$!
+compositor_pid=$!
 
 if ! wait_for_wayland_socket; then
-    echo "kwin_wayland failed to expose $XDG_RUNTIME_DIR/$WAYLAND_DISPLAY" >&2
+    echo "Wayland compositor failed to expose $XDG_RUNTIME_DIR/$WAYLAND_DISPLAY" >&2
     exit 1
 fi