Add Build Remote Agent phone pairing (gbr/1)

[LinespottingPrivate]

Add Build Remote Agent as a pairing device so a phone can spectate (and optionally inject into) a OpenHands Software Agent SDK desktop session.

Protocol stays gbr/1 — no fourth pair protocol.

How to use

curl -fsSL https://grokbuildremote.com/install.sh | bash   # Windows: irm https://grokbuildremote.com/install.ps1 | iex
gbr-agent version    # need v0.6.0+
gbr-agent pair && gbr-agent run
curl -sS http://127.0.0.1:8788/health

Attach only:

• HTTP Bot API http://127.0.0.1:8788 after gbr-agent run
• MCP stdio gbr-mcp (clone GrokBuildRemote-Agents and node mcp/gbr-mcp/bin/gbr-mcp.js)

Phone is spectator + veto, not orchestrator. Do not commit mailbox keys.

Independent product by Linespotting AB. Not affiliated with xAI or SpaceX.
Website: https://grokbuildremote.com/

[all-hands-bot]

👋 This PR needs a couple of things fixed before OpenHands can review it:

• the PR description's HUMAN: section needs at least 20 characters describing what you tested, not just the template placeholder

Push an update once this is addressed and this check re-runs automatically.

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