fix(chroma): raise ValueError when async client is passed to Chroma

[anish (anishesg)]

Closes #30704

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Passing a chromadb.AsyncHttpClient to the Chroma constructor causes a confusing AttributeError: 'coroutine' object has no attribute 'get_or_create_collection'. This happens because AsyncHttpClient is an async factory that returns a coroutine, and the sync __ensure_collection method tries to call .get_or_create_collection() on it directly.

This adds early validation in __init__ to detect two cases:

• An unawaited AsyncHttpClient(...) call (a coroutine object)
• An awaited AsyncClientAPI instance

Both now raise a ValueError with a clear message pointing the user to chromadb.HttpClient as the synchronous alternative.

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