packaging: add dev-setup.sh for live VM shell preview (9p fork mount)

Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>

packaging/dev-setup.sh

@@ -0,0 +1,35 @@
+#!/bin/sh
+# dev-setup.sh — run INSIDE the NoSignal dev VM to point the running shell at
+# this fork checkout (shared in over 9p), so host-side QML edits preview live.
+#
+# Prereq (run once per boot, needs root for the 9p mount):
+#   sudo mkdir -p /mnt/fork
+#   sudo mount -t 9p -o trans=virtio,version=9p2000.L,access=any nsfork /mnt/fork
+#
+# Then:  sh /mnt/fork/packaging/dev-setup.sh   (then Ctrl+Super+Alt+R to load it)
+#
+# Quickshell resolves `-c caelestia` from ~/.config/quickshell/caelestia BEFORE
+# /etc/xdg/quickshell/caelestia, so this symlink makes the session shell read
+# the fork. The compiled Caelestia plugin still comes from the installed package
+# (Qt qml import path), so only the layout QML is sourced from the fork.
+set -eu
+MNT=${MNT:-/mnt/fork}
+
+if [ ! -e "$MNT/shell.qml" ]; then
+  echo "fork not mounted at $MNT/shell.qml — mount the 9p share first:" >&2
+  echo "  sudo mkdir -p $MNT && sudo mount -t 9p -o trans=virtio,version=9p2000.L,access=any nsfork $MNT" >&2
+  exit 1
+fi
+
+mkdir -p "$HOME/.config/quickshell"
+# Back up any existing real dir/symlink once.
+if [ -e "$HOME/.config/quickshell/caelestia" ] && [ ! -L "$HOME/.config/quickshell/caelestia" ]; then
+  mv "$HOME/.config/quickshell/caelestia" "$HOME/.config/quickshell/caelestia.bak.$$"
+fi
+ln -sfn "$MNT" "$HOME/.config/quickshell/caelestia"
+echo ":: ~/.config/quickshell/caelestia -> $MNT  (the fork)"
+echo ":: now reload the shell to load the fork: press Ctrl+Super+Alt+R"
+echo "::   (after each host-side edit, reload again to preview — 9p doesn't"
+echo "::    auto-fire the file watcher, so the reload is manual.)"
+echo ""
+echo ":: to revert to the installed shell:  rm ~/.config/quickshell/caelestia  + reload"