chore: Move the bundle tool to .github/tools/bundle.sh

Update its repo-root path and all references (workflow, README, AGENTS.md).

AGENTS.md

@@ -31,7 +31,7 @@ gamescope and the Plasma desktop. Primary target: the Valve Steam Machine
   `krevert <component>`. Never call `kwriteconfig6` directly for settings a
   component owns. System files are backed up with `backup_file` and restored
   on disable.
-- **Single-file build.** `tools/bundle.sh` inlines `lib/*.sh` in the order of
+- **Single-file build.** `.github/tools/bundle.sh` inlines `lib/*.sh` in the order of
   the entry point's `for lib in ...; do` source loop and wraps everything
   after that loop in `main()`. Keep that loop on one line, keep all logic in
   functions, and don't rely on `SCRIPT_DIR` for anything but sourcing.