feat: verbose structured logging with [cron]/[job]/[spawn]/[mcp] prefixes

[Gonzih]

Summary

• [cron]: All cron:xxx messages renamed to [cron] xxx; new [cron] fired event at start of fire() with id, schedule, intervalMs, and prompt[:200]; [cron] registered event for each cron at startup
• [job]: All job:xxx messages renamed; [job] created adds task[:200] and branch; [job] running adds pid; [job] done adds duration_seconds and output_lines; [job] failed adds exit_code
• [spawn]: New [spawn] subprocess started (pid, cwd, driver — no token logged) and [spawn] subprocess exited (exit_code) events around every driver.spawn() call
• [mcp]: All tool:xxx log messages renamed to [mcp] xxx via bulk replacement
• Startup: [cc-agent] started with version+namespace, per-status job counts, and cron count + per-cron [cron] registered events after cronEngine.start()

All 143 existing tests pass.

Example log output:

2026-05-20T08:00:00.000Z [INFO] [cc-agent] started {"version":"0.15.14","namespace":"gonzih"}
2026-05-20T08:00:00.001Z [INFO] [cc-agent] startup {"jobs_total":3,"done":2,"failed":1}
2026-05-20T08:00:00.002Z [INFO] [cc-agent] startup {"crons_loaded":2}
2026-05-20T08:00:00.003Z [INFO] [cron] registered {"id":"abc123","schedule":"every 30m","intervalMs":1800000}
2026-05-20T08:00:01.000Z [INFO] [mcp] spawn_agent {"repo_url":"...","task":"Fix the bug..."}
2026-05-20T08:00:01.100Z [INFO] [job] created {"id":"def456","status":"cloning","repoUrl":"...","branch":null,"task":"Fix the bug..."}
2026-05-20T08:00:02.000Z [INFO] [spawn] subprocess started {"job_id":"def456","pid":12345,"cwd":"/tmp/cc-agent-def456-xxx","driver":"claude"}
2026-05-20T08:02:14.000Z [INFO] [spawn] subprocess exited {"job_id":"def456","pid":12345,"exit_code":0}
2026-05-20T08:02:14.010Z [INFO] [job] done {"id":"def456","exit_code":0,"duration_seconds":133,"output_lines":47,"cost_usd":0.12,"score":0.9}

Test plan

• npx vitest run src/cron.test.ts src/agent.test.ts src/index.test.ts — 143 tests pass
• git diff --staged reviewed — all changes match stated intent, no out-of-scope modifications

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