Add LP/v1 logprobs trace payload deserialization (FIR-21499)

[SunnySoldier357]

Summary

• Add lp_deserializer (LP/v1) and wire into fireworks_tracing for payloads.logprobs.
• Populate execution_metadata.extra.completion_logprobs and last-assistant Message.logprobs["content"] (cookbook path).
• Pop base_url from completion params in tracing_utils so it is encoded into gateway URLs only (fixes dev API routing).

Test plan

• pytest tests/adapters/test_lp_deserializer.py tests/adapters/test_fireworks_tracing_logprobs.py -q
• Manual e2e on dev (local only; not committed)
• Merge after mono gateway PR deploys to dev

Depends on gateway publishing logprobs payloads (fw-ai/fireworks).

Made with Cursor

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Note

Medium Risk
Changes trace-to-row shape and remote completion kwargs; logprobs only appear once the gateway publishes payloads, but bad LP data is isolated via warnings.

Overview
Adds LP/v1 support so Fireworks traces that include payloads.logprobs can be turned into eval rows with per-token completion logprobs, mirroring the existing R3 router-replay path.

A new lp_deserializer decodes base64 + zstd LP01 blobs into logprob scalars and optional token IDs (token IDs are dropped when any wire id is missing). convert_trace_dict_to_evaluation_row uses that data to fill execution_metadata.extra (completion_logprobs, optional completion_token_ids, logprobs_metadata) and attaches Message.logprobs["content"] on the last assistant message. Failures are logged and do not fail the whole conversion.

The test remote server no longer forwards base_url inside completion_params to the OpenAI client—routing stays on model_base_url / gateway URL encoding—aligning with how build_init_request treats base_url for tracing URLs (comment-only tweak in tracing_utils).

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