ensure logs are json serializable

[xzrderek]

Note

Improves Fireworks logging robustness by pre-serializing the request payload and handling JSON serialization errors before network calls.

• Pre-serialize payload to payloadJson with try/catch; on failure, emit error and skip send
• Reuse payloadJson for POST body and debug size logging; include serialized payload in debug error logs
• Minor: bump typescript/package.json version to 0.1.12

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