PKGBUILD: Point desktop Exec at update shim

0.30 shipped Exec="/opt/Grok Bot/grok-bot", so the app menu skipped
/usr/bin/grok-bot and never auto-updated. Always rewrite the desktop
Exec to the PATH shim after unpacking the .deb so that cannot regress.
Bump pkgrel to 2; clearer sudo failure hint in the launch shim.

README.md

@@ -58,5 +58,6 @@ Scheduled Gitea Actions will do the same and build a release package.
 ## Notes
 
 - `/usr/bin/grok-bot` (and `sand`) is a launch shim: unless `GROK_BOT_NO_UPDATE=1`, it checks the latest Gitea release and may `pacman -U` a newer `.pkg.tar.zst` before exec'ing `/opt/Grok Bot/…`. Network/API failures still launch the installed binary.
+- If the app menu still launches an old binary without updating, run `/usr/bin/grok-bot` once from a terminal, or `sudo pacman -U` the newer `.pkg.tar.zst` from Releases — the menu must call the PATH shim, not `/opt/Grok Bot/…`.
 - Upstream Linux builds still have no in-app updater for the Electron app itself; `scripts/update.sh` bumps the PKGBUILD from Cursor's feed when packaging a new upstream version.
 - `chrome-sandbox` is left non-setuid because the install path contains a space; user namespaces cover sandboxing on CachyOS.