cce v2.6.6

Fixed

• The Ollama embedder fails loud instead of degrading silently (#30). Three compounding silent
  failures in the opt-in --embedder ollama path are gone. (1) Index time: an embedding failure —
  Ollama unreachable at start, or dying mid-index — now aborts cce index with a clear error and
  writes no store (previously embed_batch swallowed errors into empty vectors, which were persisted
  and scored cosine 0 forever, invisible to vector recall). There is deliberately no fallback to the
  hash embedder at index time either: that would poison the store's declared embedder space just as
  badly. (2) Query time, CLI: cce search (and --workspace) on an ollama-built store with Ollama
  down now errors with guidance (start Ollama, or re-index with the default hash embedder) instead
  of silently embedding the query with the hash backend — cosine across two unrelated vector spaces is
  meaningless. (3) Query time, MCP: context_search follows the friendly-error pattern — it does not
  crash the session, and now degrades to keyword-only (BM25) results under a pinned NOTICE: line,
  so the agent keeps getting results while the degradation stays visible. The Embedder trait lost its
  silent-empty-vector batch path (embed_batch → fallible try_embed/try_embed_batch), the endpoint
  and model are overridable via CCE_OLLAMA_URL/CCE_OLLAMA_MODEL (which also keeps the new
  failure-policy tests hermetic — a loopback HTTP stub, never a real server), and the docs that
  described the silent fallback as a feature are rewritten. The default hash-embedder path, the
  knowledge store (hash-only), conformance.json, and all goldens are byte-identical.