`parallel` joins the agent's default features, so the HNSW bulk build uses the
thread pool: cold index build at 10K records 1152 -> ~380 ms in a same-moment
A/B (the graph is identical either way). Nothing else on the measured paths
changes — ingest, checkpoint, open and steady-state query times are the same
with the feature on or off. Adds rayon to the default dependency set; opt out
with `--no-default-features --features float16,hnsw`.
Harness: `--e2e-only` runs the end-to-end section without the index
benchmarks. Note for anyone comparing numbers: this machine's absolute timings
drifted ~1.5x over a long session, so only same-moment A/B runs are
comparable.
Co-Authored-By: Claude Fable 5.1 <[email protected]>
