Add structured JSON logging with Pino

[burner-agent]

Summary

Replace console.log/ad-hoc logging with pinojs/pino (17k+ stars) for structured JSON logging across the agent.

Motivation

Debugging autonomous RALPH loops is difficult without structured, queryable logs. Currently src/monitor.ts handles logging but a proper structured logger would make it easy to trace message lifecycles, Claude CLI invocations, self-edits, and errors with consistent format and log levels.

Proposal

• Add pino as a dependency (super fast, minimal overhead)
• Replace console.log calls with leveled pino loggers (info, warn, error, debug)
• Log key events: RALPH step start/end, Claude CLI invocation timing/tokens, queue operations, webhook events
• Output as JSON for easy parsing/querying, with pretty-print option for dev

References

• https://github.com/pinojs/pino