feat: add Reachy Mini NATS sidecar support

[armwaheed]

Summary

This PR adds a working Reachy Mini Device Connect sidecar flow for Raspberry Pi deployments that already have a local Reachy daemon or app running.

What changed

• add run_reachy_nats.py as a small Reachy NATS sidecar runner
• add transport_mode override support to ReachyMiniDriver
  • allows forcing websocket when Reachy is local to the Pi but Device Connect traffic should go over NATS
• add tests for the new transport override behavior
• rewrite the Reachy guide around the validated NATS setup
• add a pointer from the main Device Connect guide to the Reachy-specific setup

Why

The original Reachy docs were oriented around a standalone daemon flow and Zenoh examples. On the Pi we validated a different production-relevant pattern:

• an existing local Reachy app owns the daemon on 127.0.0.1:8000
• a separate Device Connect sidecar runs alongside it
• the sidecar bridges Reachy RPCs into Device Connect over NATS

Without the transport override, the driver auto-detection can select the wrong real-time transport for this topology.

Validation

Validated on a Raspberry Pi Reachy setup using:

• local Reachy daemon on 127.0.0.1:8000
• NATS broker nats://nats-nlb-52ebd3849ae4cb02.elb.us-east-1.amazonaws.com:4222

Observed successful registration logs:

• Connected to NATS broker: [...]
• Driver connected: reachy_mini
• Device registered: ...
• Subscribed to commands on device-connect.default.reachy-mini-1.cmd

Notes

The reusable Reachy Device Connect bridge remains in strands_robots/device_connect/.
App-specific Reachy browser-control behavior should stay in the separate conference-room repo.

[armwaheed]

Attn: @atsyplikhin

[armwaheed]

Follow-up: the private broker/dashboard path is now confirmed working.

The required private-broker configuration is:

export NATS_URL='nats://137.184.86.16:4222'
export TENANT='souravpati'
export DEVICE_ID='reachy-mini-1'
export NATS_CREDENTIALS_FILE='/path/to/souravpati-reachy-mini-1.creds.json'
export REACHY_HOST='127.0.0.1'
export REACHY_PORT='8000'
export REACHY_TRANSPORT_MODE='websocket'

The important correction is that device_id=reachy-mini-1 was not enough by itself. The runtime also had to use tenant=souravpati for the private broker subjects.

I pushed an additional update to this branch to:

• add TENANT support to run_reachy_nats.py
• document the exact private-broker configuration in reachy-guide.md
• mention the required tenant/device settings from the main Device Connect guide

Observed success log on the private broker:

Connected to NATS broker: ['nats://137.184.86.16:4222']
Device registered: registration_id=c47be84a-e207-4824-8eed-9980bd8f27e7
Subscribed to commands on device-connect.souravpati.reachy-mini-1.cmd