Updates the docstring + test docstring for the NotImplementedError stub
shipped in T112 (Phase 4.5). Original wording said Featherless 'does
not expose /v1/embeddings'; verified the endpoint actually responds
but always returns HTTP 500 with type='completions_error' for every
model tried (text-embedding-3-small, BAAI/bge-small-en-v1.5,
sentence-transformers/all-MiniLM-L6-v2, etc.) and /v1/models has no
embedding-class entries. Stub behavior unchanged.
Implements embed() on FeatherlessClient. Featherless's OpenAI-
compatible surface does NOT expose /v1/embeddings at the time of
writing, so this implementation raises NotImplementedError rather
than issuing a request that would 404. The
chat.services.embeddings.generate_embedding wrapper (T112.3)
catches the exception and degrades to the zero-vector fallback path
(plus the existing T107 warning) — misconfigured callers fail loudly
in logs while the request path keeps working.
If/when Featherless ships embeddings, swap the body for
self._client.embeddings.create(model=..., input=...) guarded by
the existing 2-conn semaphore (mirrors generate/stream). The Protocol
seam in T112.1 is already wired so no other code needs to change.
Adds tests/test_featherless.py pinning the NotImplementedError
contract.
Joseph Doherty