feat(github): replace hardcoded agent messages with LLM-generated ack messages

[zbigniewsobiecki]

Summary

• Unify initial GitHub comments: LLM-generated ack messages (from generateAckMessage()) are now THE initial comment for all GitHub agents, eliminating duplicate comments in router+worker mode
• Plumb ackMessage through the entire pipeline: queue → worker → webhook handler → agent execution, alongside the existing ackCommentId
• Expand ack posting to all GitHub agents: postAcknowledgmentComment() now handles review, respond-to-ci, etc. — not just respond-to-review/respond-to-pr-comment
• Reuse pre-existing ack comments: When ackCommentId is present, agents skip posting a new comment and instead record the existing one for progress updates
• Remove hardcoded headerMessage from all 4 GitHub agent definitions; INITIAL_MESSAGES serves as the static fallback
• Simplify PRResponseAgentInput: removed acknowledgmentCommentId field (unified to ackCommentId on AgentInput)

Files changed (19)

Area	Files	Change
Types	src/types/index.ts, src/router/queue.ts	Add ackMessage field
Router	src/router/github.ts	tryPostGitHubAck returns { commentId, message }
Worker	src/worker-entry.ts	Pass ackMessage through
Queue	src/utils/webhookQueue.ts, src/triggers/shared/webhook-queue.ts	Forward ackMessage
Webhook handler	src/triggers/github/webhook-handler.ts	Expand ack to all agents with generateAckMessage()
Agent core	src/agents/shared/githubAgent.ts	Reuse ack comment, resolve effective header
PR response	src/agents/shared/prResponseAgent.ts	Remove acknowledgmentCommentId
Agent defs	src/agents/review.ts, respond-to-review.ts, respond-to-pr-comment.ts, respond-to-ci.ts	Remove headerMessage
Claude Code	src/backends/agent-profiles.ts	preExecute skips when ack exists, uses ackMessage
Tests	5 test files	14 new tests, updated assertions

Test plan

• npm run typecheck — clean
• npm run lint — clean (only 1 pre-existing warning)
• npm test — all 2614 tests pass (14 new)
• New tests cover: tryPostGitHubAck return type, ack message on queued jobs, preExecute skip when ack exists, preExecute uses ackMessage fallback, ackMessage queue forwarding
• Manual verification: trigger a review agent via webhook → verify single LLM-generated comment (not two)

🤖 Generated with Claude Code