Let a connector write, and publish strings bare

Two things stopped the engine commanding this house. ConnectorNode hardwired
its node function to a no-op, so an input message reaching a connector was
discarded and Art-Net's packet builder was unreachable; write() now carries
the input ports, which is additive so the contract version holds. And the MQTT
publisher JSON-encoded every payload, so "ON" went on the wire quoted and the
devices on a shared broker, which speak bare values, ignored it.

seed_house_control.py is the rig: a flow that drives the washing machine plug,
a dimmer and a colour fixture over MQTT, carries the same two as DMX on an
Art-Net node with transmit still off, and a dashboard to drive it by hand.

Makefile

@@ -3,7 +3,7 @@
 # The workspace root delegates to these (see ../Makefile).
 
 .PHONY: dev-utils dev dev-local up down update install dev-backend dev-frontend \
-        generate-client seed-example seed-demo seed-hosted-demo test test-backend test-frontend soak bench-startup lint lint-backend \
+        generate-client seed-example seed-demo seed-house seed-hosted-demo test test-backend test-frontend soak bench-startup lint lint-backend \
         lint-frontend umami clean help
 
 COMPOSE_ROOT := $(CURDIR)
@@ -97,6 +97,9 @@ seed-example:  ## Seed the querying-chart example (needs a running stack + Influ
 seed-demo:  ## Seed the training-run example: a batch flow and its dashboard
 	cd backend && uv run python ../scripts/seed_demo_training.py
 
+seed-house:  ## Seed the house write-path rig (needs the real broker reachable)
+	cd backend && uv run python ../scripts/seed_house_control.py
+
 # Operators of the hosted demo only — NOT part of any deployment, and nothing a
 # self-hosted instance needs. It wipes and recreates its three flows and its
 # dashboard, so re-running it is how the public demo is reset.