Add grok-bot 0.18.0

Package the official Grok Bot Linux .deb (internal name: sand) for Arch.
Wraps /opt/Grok Bot/sand with a Wayland launcher and grok-bot desktop entry.

Linux has no latest feed; update-pkgver.sh resolves version+commit from the
darwin-arm64 sand feed and HEAD-checks the Linux deb before pinning.

pkgbuilds/grok-bot/.omarchy/package.json

@@ -0,0 +1,5 @@
+{
+  "source": "aur",
+  "sync": false,
+  "upstream_commit": "05eb78fca06b482affda28b26223cbf249d4bbcd"
+}