[Dazzanova]

For issue #596

Summary

• Add logger.child(fields) to bind structured fields to log entries.
• Support nested child loggers and per-call field overrides.
• Preserve safe serialization for reserved keys, functions, and throwing getters.
• Add unit tests and document the new API.

Testing

• Focused runtime logger tests: 20 passed.
• Formatting and lint checks: passed after fixing the reported lint errors.
• Full workspace checks: previously reported unrelated-looking playground configuration and type-resolution failures.