Add a rate-limited Meilisearch embedder capability check and surface a
semantic-coverage block in the admin search status.
Capability validation confirms the active index declares the configured
embedder with source="userProvided" and dimensions matching the canonical
embedding dimension, then runs a unit-vector hybrid probe to confirm the
index accepts the request shape. The whole path (GetSettings + evaluate +
probe) is cached for 5m and NEVER trips the circuit, marks a fallback, or
modifies unhealthyUntil, so a misconfigured embedder cannot take keyword
search down. The pure evaluator (evaluateEmbedderSettings) is unit-tested
across missing/wrong-source/wrong-dimensions/ok with distinct reasons.
The admin status gains a Semantic block read entirely from the in-memory
coverage snapshot (Snapshot + CoverageReady) with no new DB query in
Status(); document_count/vector_document_count are unchanged (additive
only). buildSemanticStatus is pure and unit-tested (nil snapshot and a
populated, deterministically-sorted snapshot).
Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>
