fix(auth): set active_provider after hermes auth add google-gemini-cli

hermes auth add google-gemini-cli called pool.add_entry() but never wrote
to providers["google-gemini-cli"] or set active_provider in auth.json.
_model_section_has_credentials() checks get_active_provider() first; with
active_provider unset and no api_key_env_vars configured for oauth_external
providers, the setup wizard reported "No inference provider configured" even
after a successful OAuth login.

Add _mark_google_gemini_cli_active() in auth.py: writes a minimal provider
state entry (email for display only) and calls _save_provider_state() to set
active_provider. The function deliberately does not copy access_token or
refresh_token — those are managed by agent.google_oauth in the Google
credential file and must not be duplicated in auth.json where they would
become stale.

pool.add_entry() is retained so "hermes auth list" continues to show the entry.
Runtime credential resolution continues to use agent.google_oauth directly.

Mirrors the fix applied to openai-codex (#37517) and xai-oauth (#37576).

hermes_cli/auth_commands.py

@@ -353,6 +353,7 @@ def auth_add_command(args) -> None:
         from agent.google_oauth import run_gemini_oauth_login_pure
 
         creds = run_gemini_oauth_login_pure()
+        auth_mod._mark_google_gemini_cli_active(creds)
         label = (getattr(args, "label", None) or "").strip() or (
             creds.get("email") or _oauth_default_label(provider, len(pool.entries()) + 1)
         )