Add Build Remote Agent phone pairing (gbr/1)

[LinespottingPrivate]

What

Docs-only adapter so Mobilerun users can pair Build Remote Agent as a phone spectator on the desktop coding-agent host.

GBR is phone spectator for DESKTOP agents, not a replacement for Mobilerun device control. Companion: pair the coding-agent host via gbr-agent.

Phone is spectator + veto, not orchestrator. Attach only http://127.0.0.1:8788 or stdio gbr-mcp. No mailbox keys. Protocol gbr/1.

Files: docs/gbr.md, README.md

How

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

Windows: irm https://grokbuildremote.com/install.ps1 | iex

Independent product by Linespotting AB. Not affiliated with xAI or SpaceX.
Agent: https://github.com/LinespottingOrg/GrokBuildRemote-Agents (MIT)