LUME ↔ mesh integration

LUME ↔ mesh integration

Decision: NOT a meshd slot

`[home-path]` slots spawn short-lived LLM agent CLIs (claude, codex,
gemini). LUME is a persistent device running `lume-daemon` as a systemd
unit. Wrong abstraction.

What LUME does instead

1. Announce itself on boot by posting `mesh_events.devices.online` with
`{device: "lume-01", tailscale_ip, sensors: [...], ts}` to NATS on the
cloud-vm leaf node.
2. Heartbeat every 10s to `mesh_events.devices.heartbeat` with FPS +
thermal snapshot (same payload as `lume.health` topic).
3. Bidirectional control subscribed to `mesh_commands.lume.*` — other
mesh agents can request screenshots, LED changes, depth bags.
4. Dashboard at Nexus `/lume` pulls the device's WS directly over
Tailscale (`ws://lume.local:9570/ws`).

Wire-up order (Friday)

1. Jetson joins Tailscale net
2. `lume-daemon` starts under systemd, binds `:9570`
3. One-shot `scripts/announce-to-mesh.sh` posts the online event
4. Nexus `/lume` page picks it up from `mesh_events` subscription