feat: enhance Home Assistant integration with service discovery and setup

Improvements to the HA integration merged from PR #184:

- Add ha_list_services tool: discovers available services (actions) per
  domain with descriptions and parameter fields. Tells the model what
  it can do with each device type (e.g. light.turn_on accepts brightness,
  color_name, transition). Closes the gap where the model had to guess
  available actions.

- Add HA to hermes tools config: users can enable/disable the homeassistant
  toolset and configure HASS_TOKEN + HASS_URL through 'hermes tools' setup
  flow instead of manually editing .env.

- Fix should-fix items from code review:
  - Remove sys.path.insert hack from gateway adapter
  - Replace all print() calls with proper logger (info/warning/error)
  - Move env var reads from import-time to handler-time via _get_config()
  - Add dedicated REST session reuse in gateway send()

- Update ha_call_service description to reference ha_list_services for
  action discovery.

- Update tests for new ha_list_services tool in toolset resolution.

hermes_cli/tools_config.py

@@ -36,6 +36,7 @@ CONFIGURABLE_TOOLSETS = [
     ("delegation",      "👥 Task Delegation",           "delegate_task"),
     ("cronjob",         "⏰ Cron Jobs",                 "schedule, list, remove"),
     ("rl",              "🧪 RL Training",               "Tinker-Atropos training tools"),
+    ("homeassistant",    "🏠 Home Assistant",           "smart home device control"),
 ]
 
 # Platform display config
@@ -312,6 +313,8 @@ TOOLSET_ENV_REQUIREMENTS = {
     "tts":        [],  # Edge TTS is free, no key needed
     "rl":         [("TINKER_API_KEY",       "https://tinker-console.thinkingmachines.ai/keys"),
                    ("WANDB_API_KEY",        "https://wandb.ai/authorize")],
+    "homeassistant": [("HASS_TOKEN", "Home Assistant > Profile > Long-Lived Access Tokens"),
+                      ("HASS_URL",   None)],
 }