Function resolve_query_embedding 

pub fn resolve_query_embedding(
    fallback_fts_only: bool,
    models_dir: &Path,
    query: &str,
    backends: BackendChoice,
    log_target: &'static str,
) -> QueryEmbedding

Resolves the query embedding, degrading to FTS5-only instead of failing.

When the live embedding cannot be produced — timeout, rate limit, unreachable provider — the read still returns results, ranked by BM25 alone. The caller surfaces that through vec_degraded and vec_error on the envelope, so the degradation is visible rather than silent.

--fallback-fts-only takes the same path deliberately and never contacts the provider at all.

log_target is the tracing target of the calling subcommand, so a degraded read stays attributable to the command the operator actually ran.