Phase 7: rename SkyOS → OrionOS across entire codebase

- Rename all binaries: skywm→orionwm, skydeskbar→oriondeskbar,
  skylauncher→orionlauncher, skyinstall/skyinstall-gui→orioninstall*
- Rename theme directory: themes/SkyOS/ → themes/OrionOS/
- Update all string literals, window titles, menu labels, and comments
- Update ISO build: hostname→orionos, user→orion, all paths/labels
- Add Plymouth boot splash theme (orionos) with Navy+Blue palette
- Update GTK2/GTK3 theme names, wallpaper output name
- Update .gitignore, root Makefile, build-iso.sh for new binary names

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

Makefile

@@ -1,4 +1,4 @@
-# SkyOS — top-level build
+# OrionOS — top-level build
 # Usage:
 #   make          — build all components
 #   make install  — install binaries + theme to /usr/local
@@ -29,26 +29,26 @@ clean:
 
 install: all
 	# binaries
-	install -Dm755 wm/skywm              /usr/local/bin/skywm
-	install -Dm755 deskbar/skydeskbar    /usr/local/bin/skydeskbar
-	install -Dm755 launcher/skylauncher  /usr/local/bin/skylauncher
-	install -Dm755 themes/skywallpaper   /usr/local/bin/skywallpaper
+	install -Dm755 wm/orionwm              /usr/local/bin/orionwm
+	install -Dm755 deskbar/oriondeskbar    /usr/local/bin/oriondeskbar
+	install -Dm755 launcher/orionlauncher  /usr/local/bin/orionlauncher
+	install -Dm755 themes/orionwallpaper   /usr/local/bin/orionwallpaper
 	# GTK theme
 	mkdir -p /usr/share/themes
-	cp -r themes/SkyOS /usr/share/themes/
+	cp -r themes/OrionOS /usr/share/themes/
 	# picom config
-	install -Dm644 themes/picom.conf /etc/skyos/picom.conf
+	install -Dm644 themes/picom.conf /etc/orionos/picom.conf
 	# wallpaper
-	mkdir -p /usr/share/skyos/wallpapers
+	mkdir -p /usr/share/orionos/wallpapers
 	bash themes/wallpapers/generate-default.sh || true
-	cp -f themes/wallpapers/skyos-default.png /usr/share/skyos/wallpapers/ 2>/dev/null || true
+	cp -f themes/wallpapers/skyos-default.png /usr/share/orionos/wallpapers/ 2>/dev/null || true
 	@echo ""
-	@echo "SkyOS installed. Add this to ~/.xinitrc to start:"
+	@echo "OrionOS installed. Add this to ~/.xinitrc to start:"
 	@echo ""
-	@echo "  skywallpaper"
-	@echo "  picom --config /etc/skyos/picom.conf &"
-	@echo "  skydeskbar &"
-	@echo "  exec skywm"
+	@echo "  orionwallpaper"
+	@echo "  picom --config /etc/orionos/picom.conf &"
+	@echo "  oriondeskbar &"
+	@echo "  exec orionwm"
 
 iso:
 	chmod +x build-iso.sh