Doorbell greeting: roll to the door and say hello

Home assistants meet robots at the front door. Subscribe to a doorbell webhook or MQTT topic, navigate to a saved "entry" pose, speak a short TTS greeting, and open a low-res stream. Useful for packages and kids coming home; weird for strangers — add a schedule and an allowlist.

Curated seed / example for mapped wheeled platforms.

Don't open physical doors with the robot. This is greeting + awareness only.