Phase 4-6: Quill editor, Lens viewer, Rigel context menu, CI, website

Phase 4 — native apps:
- quill/: text editor (monospace, double-buffered, find bar, undo, open/save)
- lens/: image viewer using imlib2 (zoom, pan, rotate, directory nav)
- wm/src/menu.c: launch quill instead of mousepad
- iso/docker/entrypoint.sh: add imlib2 package; install quill + lens binaries
- skykit/template/: developer app template demonstrating the SkyKit API

Phase 5 — file system and search:
- rigel/rigel.c: right-click context menu (open, open in quill, copy path,
  rename, trash, properties); Ctrl+F search/filter bar with name highlighting;
  F2 rename-in-place overlay; Delete key moves to trash

Phase 6 — distribution:
- .github/workflows/build-iso.yml: GitHub Actions CI that compiles all
  components and builds a bootable ISO on every tag push; creates a GitHub
  release with sha256 checksums

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

Makefile

@@ -5,9 +5,9 @@
 #   make clean    — remove build artifacts
 #   make iso      — build the bootable ISO (requires Arch Linux + archiso)
 
-.PHONY: all wm deskbar launcher installer nebula orionpkg skykit rigel clean install iso
+.PHONY: all wm deskbar launcher installer nebula orionpkg skykit rigel quill lens clean install iso
 
-all: wm deskbar launcher installer nebula orionpkg skykit rigel
+all: wm deskbar launcher installer nebula orionpkg skykit rigel quill lens
 
 wm:
 	$(MAKE) -C wm
@@ -33,6 +33,12 @@ skykit:
 rigel:
 	$(MAKE) -C rigel
 
+quill:
+	$(MAKE) -C quill
+
+lens:
+	$(MAKE) -C lens
+
 clean:
 	$(MAKE) -C wm        clean
 	$(MAKE) -C deskbar   clean
@@ -42,6 +48,8 @@ clean:
 	$(MAKE) -C orionpkg  clean
 	$(MAKE) -C skykit    clean
 	$(MAKE) -C rigel     clean
+	$(MAKE) -C quill     clean
+	$(MAKE) -C lens      clean
 
 install: all
 	# binaries
@@ -52,6 +60,8 @@ install: all
 	install -Dm755 nebula/nebula           /usr/local/bin/nebula
 	install -Dm755 orionpkg/orionpkg       /usr/local/bin/orionpkg
 	install -Dm755 rigel/rigel             /usr/local/bin/rigel
+	install -Dm755 quill/quill             /usr/local/bin/quill
+	install -Dm755 lens/lens               /usr/local/bin/lens
 	# GTK theme
 	mkdir -p /usr/share/themes
 	cp -r themes/OrionOS /usr/share/themes/