Discovery adapter: Claude Code (JSONL)

[leefaus]

Part of #11

Summary

Implement TraceDiscovery for Claude Code. Reads trace history from ~/.claude/ JSONL files.

Storage Details

Aspect	Detail
Storage path	~/.claude (overridable via env var)
Detection	.claude, .claude/settings.json
History file	~/.claude/history.jsonl
Project sessions	~/.claude/projects/<project_hash>/<session_id>.jsonl
Format	JSONL — one JSON object per line

Event Parsing

• Roles: user, assistant
• Tool events: blocks with type: "tool_use", type: "tool_result", linked via tool_use_id
• Thinking: extended thinking blocks

Notes

Claude Code already has a real-time AgentHook in hooks/claude_code.rs. This discovery adapter enables:

1. Backfilling traces from before Atomic was installed
2. Post-record hook matching (find which trace was active during a recording)

Acceptance Criteria

• list_traces() enumerates sessions from ~/.claude/projects/
• read_events() parses JSONL into DiscoveredEvents with correct types
• Tool calls include tool_name, tool_call_id, and are classifiable
• Unit tests with JSONL fixture files

Estimated Effort

0.5-1 day