AgentSea.Embedder.OpenAI (agentsea_embeddings v0.1.0)

OpenAI embeddings adapter (POST /v1/embeddings) over Req — a remote AgentSea.Embedder (no local model).

Options: :api_key (defaults to OPENAI_API_KEY), :model (default text-embedding-3-small), :base_url, :adapter (a Req adapter for tests). dimensions/0 reads config :agentsea_embeddings, :openai_dimensions (default 1536 — must match the model).