CRITICAL: random-100-match-kw-small-vocab declares vector_count 100 for a 1M corpus — shared-corpus mode uploads 100 docs and reports success #224

Found by a 7-agent adversarial parity review; verified directly.

datasets/datasets.json:

random-100-match-kw-small-vocab-filters     vector_count=100        path=.../random_keywords_1m_vocab_10
random-100-match-kw-small-vocab-no-filters  vector_count=100        path=.../random_keywords_1m_vocab_10_no_filters
random-match-keyword-100-angular-filters    vector_count=1000000    path=.../random_keywords_1m
random-match-keyword-100-angular-no-filters vector_count=1000000    path=.../random_keywords_1m_no_filters

The two small-vocab entries point at a 1,000,000-point corpus (random_keywords_1m_vocab_10) while declaring vector_count: 100. Their siblings on the same corpus family declare 1000000 correctly. This looks like a copy-paste from the genuine random-100 entry directly above.

vector_count is not decorative. src/bin/vector_db_benchmark/engine/redis.rs:1901-1922 uses it as the shared-corpus completeness gate:

if let Some(expected) = dataset.config.vector_count.filter(|&n| n > 0) {

With shared-corpus mode enabled (redis.rs:249, driven by shared_key_prefix()), the upload is skipped as soon as existing >= expected — i.e. after 100 keys — and prints "Shared corpus already populated … skipping re-upload". The sweep then measures recall over ~100 documents against 1M-point ground truth. Recall collapses to ~0 with no error surfaced.

Fix: set both to 1000000. Then add a guard so this class cannot recur — e.g. validate vector_count against the actual corpus on first download, or fail loudly when the completeness gate is satisfied by an implausibly small fraction of a declared corpus.

Two more vector_count values are wrong in the benign (over-declaring) direction, measured from the on-disk NPY headers — worth fixing in the same PR since --list-datasets reports them:

• arxiv-titles-384-angular-*: declared 2205995, actual (2138591, 384)
• h-and-m-2048-angular-*: declared 105542, actual (105100, 2048)