feat: add ggcoder ACP adapter and Dockerfile

[Joseph19820124]

Summary

Integrates @kenkaiiii/ggcoder into OpenAB by adding a minimal ACP adapter, following the same pattern as the Codex integration.

ggcoder does not support ACP natively — it exposes a custom --rpc JSON-over-stdio protocol. This PR adds a thin Node.js adapter (ggcoder-acp) that bridges OpenAB's JSON-RPC 2.0 ACP protocol to ggcoder's --rpc mode.

Changes

File	Description
ggcoder-acp/	ACP adapter package — handles initialize, session/new, session/load, session/prompt, session/set_config_option; streams text_delta and tool_call events as ACP notifications
Dockerfile.ggcoder	Multi-stage image (Rust builder + node:22-bookworm-slim) — installs @kenkaiiii/ggcoder and ggcoder-acp globally; follows Dockerfile.codex pattern
docs/ggcoder.md	Setup guide: Docker, Helm, manual config.toml, OAuth + API key auth, model switching, troubleshooting
charts/openab/values.yaml	Adds commented-out ggcoder agent block alongside existing opencode/cursor examples

Usage

config.toml

[agent]
command = "ggcoder-acp"
args    = []
working_dir = "/home/node"

Helm

helm install openab openab/openab \
  --set agents.kiro.enabled=false \
  --set agents.ggcoder.discord.enabled=true \
  --set agents.ggcoder.discord.botToken="$DISCORD_BOT_TOKEN" \
  --set-string 'agents.ggcoder.discord.allowedChannels[0]=YOUR_CHANNEL_ID' \
  --set agents.ggcoder.image=ghcr.io/openabdev/openab-ggcoder:latest \
  --set agents.ggcoder.command=ggcoder-acp \
  --set agents.ggcoder.workingDir=/home/node

Protocol mapping

ACP method	ggcoder --rpc command
initialize	(static reply, no ggcoder call)
session/new	new_session
session/load	new_session (ggcoder has no persistent load)
session/prompt	prompt + stream text_delta/tool_call_* events
session/set_config_option	switch_model (for model/provider)

Tested

• Adapter starts and responds to initialize correctly
• session/new spawns ggcoder and returns a session ID
• session/prompt streams text deltas as session/textDelta ACP notifications

[github-actions]

⚠️ This PR is missing a Discord Discussion URL in the body.

All PRs must reference a prior Discord discussion to ensure community alignment before implementation.

Please edit the PR description to include a link like:

Discord Discussion URL: https://discord.com/channels/...

This PR will be automatically closed in 3 days if the link is not added.