fix(honcho): read HONCHO_BASE_URL for local/self-hosted instances

Cherry-picked from PR #2120 by @unclebumpy.

- from_env() now reads HONCHO_BASE_URL and enables Honcho when base_url
  is set, even without an API key
- from_global_config() reads baseUrl from config root with
  HONCHO_BASE_URL env var as fallback
- get_honcho_client() guard relaxed to allow base_url without api_key
  for no-auth local instances
- Added HONCHO_BASE_URL to OPTIONAL_ENV_VARS registry

Result: Setting HONCHO_BASE_URL=http://localhost:8000 in ~/.hermes/.env
now correctly routes the Honcho client to a local instance.

hermes_cli/config.py

@@ -670,6 +670,11 @@ OPTIONAL_ENV_VARS = {
         "password": True,
         "category": "tool",
     },
+    "HONCHO_BASE_URL": {
+        "description": "Base URL for self-hosted Honcho instances (no API key needed)",
+        "prompt": "Honcho base URL (e.g. http://localhost:8000)",
+        "category": "tool",
+    },
 
     # ── Messaging platforms ──
     "TELEGRAM_BOT_TOKEN": {