fix: ga scripts prefer project .venv over system python

Prefer project virtualenv Python in ga launchers to avoid PEP 668/system Python issues, falling back to PATH python when no venv exists.

ga_cli/ga_cli.cmd

@@ -1,3 +1,5 @@
 @echo off
 cd /d "%~dp0.."
-python -m ga_cli %*
+set "PY=.venv\Scripts\python.exe"
+if not exist "%PY%" set "PY=python"
+"%PY%" -m ga_cli %*