Summary

• Add HASS_TOOL_URL / HASS_TOOL_TOKEN for the Home Assistant tool surface.
• Add HASS_PLATFORM_URL / HASS_PLATFORM_TOKEN for the Home Assistant websocket platform.
• Add HASS_PLATFORM_DISABLE=1 to allow tool-only Home Assistant setups.
• Preserve legacy HASS_URL / HASS_TOKEN as the shared fallback for both surfaces.
• Clean up partially opened Home Assistant websocket resources when connect fails midway.

Why

Some deployments want Hermes tools to talk to a local Home Assistant proxy while not enabling the gateway websocket platform, or want the platform and tools to use different credentials/URLs. Today both surfaces are forced through the same HASS_URL / HASS_TOKEN values.

This keeps existing behavior by default while allowing safer tool-only/proxy deployments.

Test plan

uv run --extra dev pytest \
  tests/gateway/test_homeassistant.py \
  tests/tools/test_homeassistant_tool.py \
  tests/tools/test_send_message_missing_platforms.py -q

Result: 139 passed, 1 existing RuntimeWarning about _async_call_service.