feat: AI-summarized handoff prompts for completed jobs

[nigel-dev]

Source

Audit report — Section 9: Phase 3 Roadmap + Section 4: Ecosystem Patterns (opencode-handoff)

Description

When a job completes, its context (what it did, what decisions it made, what files it changed) is lost unless the user manually inspects via mc_capture and mc_diff. The main session AI has no structured summary of the completed work.

Ecosystem Precedent

opencode-handoff generates AI-summarized context with synthetic file preloading for session continuity. This pattern is directly transferable to MC's job completion flow.

Proposed Solution

1. Auto-generate handoff summary when a job completes:
   • Files changed (git diff --name-only)
   • Commit messages from the job's branch
   • Key decisions or notes from mc_report messages
   • Terminal output summary (last N lines or AI-summarized)
2. Inject into main session context so the AI naturally knows what happened
3. Store for reference in job state for later retrieval
4. Use in PR bodies — feed handoff summaries into feat: PR narrative synthesis from job data, diffs, and reports #22 (PR narrative synthesis)

Relationship to Other Issues

• Builds on feat: PR narrative synthesis from job data, diffs, and reports #22 (PR narrative synthesis) — handoff summaries are input to PR bodies
• Builds on feat: Capture failure artifacts on job failure (terminal output, diff, env) #23 (failure artifacts) — similar data collection, different trigger
• Complements existing compaction context injection (rich job cards in compaction.ts)