feat: initial noctalia-greeter release

QuickShell QML login greeter for greetd, styled after noctalia-shell
lockscreen. Runs under niri compositor as _greeter user. Theme is
live-synced from noctalia config via runit service.

- shell.qml: QuickShell greeter UI + greetd auth flow
- sync/: inotifywait theme sync daemon + runit service
- greetd/: niri compositor config + wrapper scripts
- install.sh: deployment helper
- test/check-syntax.sh: 19 syntax/structural checks (0 failures)

Co-authored-by: Copilot <223556219+Copilot@users.noreply.github.com>

install.sh

@@ -0,0 +1,39 @@
+#!/bin/sh
+# install.sh — deploy noctalia-greeter to system paths
+set -e
+
+REPO_DIR="$(cd "$(dirname "$0")" && pwd)"
+
+if [ "$(id -u)" -ne 0 ]; then
+    echo "Run as root: sudo ./install.sh" >&2
+    exit 1
+fi
+
+echo "==> Installing noctalia-greeter..."
+
+# QuickShell config (read by qs as _greeter)
+install -Dm644 "$REPO_DIR/shell.qml" /home/moze/.config/noctalia-greeter/shell.qml
+chown moze:moze /home/moze/.config/noctalia-greeter/shell.qml
+
+# Sync daemon
+install -Dm755 "$REPO_DIR/sync/noctalia-greeter-sync" /usr/local/bin/noctalia-greeter-sync
+
+# Runit service
+install -Dm755 "$REPO_DIR/sync/run" /etc/sv/noctalia-greeter-sync/run
+
+# Greeter compositor config
+install -Dm644 "$REPO_DIR/greetd/niri-greeter.kdl" /etc/greetd/niri-greeter.kdl
+install -Dm755 "$REPO_DIR/greetd/start-greeter.sh" /etc/greetd/start-greeter.sh
+
+# Theme staging dir
+install -d -m755 /var/lib/noctalia-greeter-theme
+chown moze:moze /var/lib/noctalia-greeter-theme
+
+echo ""
+echo "==> Next steps:"
+echo "  1. Edit /etc/greetd/config.toml (see greetd/config.toml.example)"
+echo "  2. Enable sync service: ln -s /etc/sv/noctalia-greeter-sync /var/service/"
+echo "  3. Run initial sync: su -s /bin/sh moze -c /usr/local/bin/noctalia-greeter-sync &"
+echo "  4. Restart greetd: sv restart greetd"
+echo ""
+echo "Done."