Run the input-method scripts with the system Python

A bare python resolves through PATH, so a mise, pyenv or venv interpreter
could run them without the system's PyGObject.

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>

shell/Commons/InputMethodState.qml

@@ -16,7 +16,7 @@ Singleton {
   // One reader and pending selection for every monitor's keyboard widget.
   Process {
     id: watcher
-    command: ["/usr/bin/python", Quickshell.env("OMARCHY_PATH") + "/default/input-methods/indicator.py"]
+    command: ["/usr/bin/python3", Quickshell.env("OMARCHY_PATH") + "/default/input-methods/indicator.py"]
     running: true
     stdinEnabled: true
     stdout: SplitParser {