fix issue with langsmith-fetch thread {id} and env precendence

[Chris Ruppelt (Cruppelt)]

Repro. This shouldn't have been calling metadata information.

langsmith-fetch thread dbc35225c9e34f6b9ea5c33a762196e2 --project-uuid 204cd3ed-77f5-4874-a01b-3a2aa6a3a2b5 --format pretty
Warning: Failed to fetch metadata for thread dbc35225c9e34f6b9ea5c33a762196e2: Failed to POST /runs/query in LangSmith API. HTTPError('400 Client Error: Bad Request for url: https://api.smith.langchain.com/runs/query', '{"detail":"Attribute extra.metadata.thread_id not accepted."}')
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Message 1: user
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Book
FXO-DDI 26-06-04 XAUUSD>=4875 GBPUSD<=1.337 DB $5m

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config should be a fallback to env vars