Add GitHub Copilot CLI support with separate Docker image

[thepagent]

Summary

Add a separate Docker image for GitHub Copilot CLI as an agent backend.

Copilot CLI has official ACP support (public preview) via copilot --acp over stdio.

Approach

• Separate Dockerfile (Dockerfile.copilot)
• Publish as ghcr.io/thepagent/agent-broker-copilot
• Auth: GitHub Copilot license (likely via gh CLI auth or GITHUB_TOKEN)

Helm usage

image:
  repository: ghcr.io/thepagent/agent-broker-copilot
agent:
  command: copilot
  args: ["--acp"]

Reference

• ACP support in Copilot CLI announcement
• ACP documentation

Related: #14, #15, #16, #18

[thepagent]

Update: Confirmed native ACP

Per OpenClaw's acpx registry, Copilot CLI has native ACP support:

agent:
  command: copilot
  args: ["--acp", "--stdio"]

Note: Copilot uses --acp --stdio (not just --acp).

Reference

• OpenClaw acpx built-in agent commands

[chaodu-agent]

Same question as #18 — could you share the use case?

1. Who is asking for Copilot CLI support? Is there a team or user currently blocked on this?
2. Has anyone tested copilot --acp with OpenAB's stdio JSON-RPC flow? The announcement link confirms ACP support exists, but real-world validation would help.
3. What's the auth story in headless/container environments? Copilot requires a GitHub Copilot license — how would this work inside a K8s pod?

A confirmed working example or a specific user request would help move this forward.

[CHC-Agent]

Issue at a Glance

Discord User ──► openab ──► Copilot CLI (ACP)
                               copilot --acp --stdio

Hi @thepagent,

ACP support confirmed by @thepagent — copilot --acp --stdio is the correct invocation. PR #88 by @bcc2xp is already in progress for the Docker image.

Remaining open items from @chaodu-agent's questions: who's the target user, and has anyone validated the full stdio JSON-RPC flow end-to-end with OpenAB? Once confirmed, this should be ready to move forward.