fix(update): look up git through the hermes_platform resolver

expose_pm_git() probed with a bare shutil.which, which the managed-runtime
resolution guard rejects outside hermes_platform/. Route the lookup through
hermes_platform.resolver.locate_command instead.

hermes_cli/_subprocess_compat.py

@@ -383,7 +383,11 @@ def expose_pm_git() -> None:
     the PATH. A machine with a working git is untouched. Raises what
     ``pm.ensure`` raises.
     """
-    if sys.platform != "win32" or shutil.which("git"):
+    if sys.platform != "win32":
+        return
+    from hermes_platform.resolver import locate_command
+
+    if locate_command("git").found:
         return
     from pm import ensure