docs(auth): replace stale 'hermes login' references with 'hermes auth add'

'hermes login' was removed (the command now just prints a deprecation
message and exits). The bundled hermes-agent SKILL.md, in-code error
messages, the tip rotation, the proxy adapters, and the docs site
still pointed agents and users at the dead command — so models loading
the skill kept running 'hermes login --provider openai-codex' and
getting a dead-end print.

Replacements use the canonical 'hermes auth add <provider>' surface
(or bare 'hermes auth' for the interactive manager).

Files:
- skills/autonomous-ai-agents/hermes-agent/SKILL.md (+ regenerated docs page)
- hermes_cli/tips.py (tip rotation)
- agent/google_oauth.py (gemini-cli error message)
- agent/conversation_loop.py (nous re-auth troubleshooting line)
- agent/credential_sources.py (docstring)
- hermes_cli/proxy/cli.py + hermes_cli/proxy/adapters/nous_portal.py (proxy auth hints)
- tests/hermes_cli/test_proxy.py (updated assertions)
- website/docs/reference/faq.md, website/docs/user-guide/features/subscription-proxy.md
- zh-Hans i18n mirrors for the above

'hermes logout' is still a live command and is left untouched.
The 'hermes login' stub in hermes_cli/auth.py:login_command() and
the cli-commands.md 'Deprecated' rows are intentionally kept as
the discoverable deprecation surface.

agent/google_oauth.py

@@ -656,7 +656,7 @@ def get_valid_access_token(*, force_refresh: bool = False) -> str:
     creds = load_credentials()
     if creds is None:
         raise GoogleOAuthError(
-            "No Google OAuth credentials found. Run `hermes login --provider google-gemini-cli` first.",
+            "No Google OAuth credentials found. Run `hermes auth add google-gemini-cli` first.",
             code="google_oauth_not_logged_in",
         )