feat(plugin): render session impact report in stop hook

[JeremyDev87]

Summary

• Add _render_impact_report(session_id, project_dir) to stop hook that reads impact-events.jsonl directly (MCP server may already be stopping)
• Aggregates events and renders box-formatted report: issues prevented (by domain), agents dispatched, checklists applied, mode transitions
• Only shown for sessions >= 30s with at least 1 impact event; all errors wrapped in try-except

Test plan

• Unit test: function returns correct box with sample JSONL events
• Unit test: returns empty string when no matching session
• Unit test: returns empty string when JSONL file missing
• typecheck passes
• 5326/5329 tests pass (1 pre-existing TUI test failure unrelated to this change)

Closes #1064

[vercel]

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Project	Deployment	Actions	Updated (UTC)
codingbuddy-landing	Ready	Preview, Comment	Mar 28, 2026 8:30am

[JeremyDev87]

Review: APPROVE

CI Status

• ✅ ALL 27/27 checks PASS — including e2e-plugin-hooks (3.11, 3.12), e2e-plugin-docker, unit-test-check

Code Quality

• ✅ Error handling — outer try/except Exception: pass wraps entire impact report block (never blocks stop hook)
• ✅ Inner error handling — json.JSONDecodeError/KeyError caught per-line in JSONL parsing
• ✅ No unused imports — json and os already imported in stop.py
• ✅ No blocking operations — synchronous JSONL file read is appropriate for stop hook (small file, local I/O)
• ✅ Clean function separation — _render_impact_report() is a pure function (reads file, returns string)

Spec Compliance (#1064)

Requirement	Status
Read events from impact-events.jsonl	✅ os.path.join(project_dir, "docs", "codingbuddy", "impact-events.jsonl")
Filter by session_id	✅ evt.get("sessionId") == session_id
Session < 30s guard	✅ if duration_secs >= 30
Events >= 1 only	✅ Returns "" if no events or no rows
JSONL file missing = no error	✅ if not os.path.isfile(jsonl_path): return ""
Append after summary	✅ summary += "\n\n" + report
Box rendering format	✅ Matches spec (╭─╮, │...│, ├─┤, ╰─╯)
All errors caught	✅ Outer try/except + inner per-line try/except

Event Aggregation

• ✅ issue_found / issue_prevented → issues_prevented count + by domain
• ✅ agent_dispatched → count
• ✅ checklist_generated → count + domains
• ✅ mode_activated → mode transitions chain

Issues Found: 0

Recommendation

APPROVE — 깔끔한 구현. 방어적 에러 처리가 철저하고, stop hook 중단 가능성 없음. JSONL 직접 읽기는 MCP 서버 종료 중에도 작동하는 올바른 설계 선택. 머지 준비 완료.