RVF SDK silently drops metadata; native metadata is not durable or returned

Versions

• @ruvector/rvf@0.2.3
• @ruvector/rvf-node@0.2.0
• darwin-arm64 native binary 0.1.7
• Node 26.4.0, macOS arm64

Public SDK reproduction

const db = await RvfDatabase.create(path, {
  dimensions: 2,
  metric: 'cosine',
}, 'node');

await db.ingestBatch([
  { id: 'red-item', vector: new Float32Array([1, 0]), metadata: { color: 'red' } },
  { id: 'blue-item', vector: new Float32Array([0, 1]), metadata: { color: 'blue' } },
]);

Observed:

• Ingest reports both vectors accepted.
• Unfiltered results contain no metadata.
• A field-0 equality filter for red returns no results.

Native N-API reproduction

Using the low-level binding, pass one positional metadata record per vector:

db.ingestBatch(
  new Float32Array([1, 0, 0, 1]),
  [101, 102],
  [
    { fieldId: 0, valueType: 'string', value: 'red' },
    { fieldId: 0, valueType: 'string', value: 'blue' },
  ],
);

A field-0 red filter works while that database instance remains open. However:

• Results still contain only ID and distance.
• After close/reopen, the same filter returns no results.

Root cause

• npm/packages/rvf/src/backend.ts accepts RvfIngestEntry.metadata but calls native ingestBatch(flat, ids) without metadata.
• Native SearchResult contains only ID/distance.
• Runtime inserts metadata into an in-memory MetadataStore, but no metadata segment is written and reloaded.
• The SDK filter declaration omits the native parser's required valueType.

Impact

Applications can successfully ingest records while silently losing metadata. Filtering may appear to work through the native API and then stop working after restart, which can produce incomplete or incorrect search results without an error.

Requested fix

As an immediate safety measure, reject non-empty SDK metadata until it is supported rather than silently accepting it.

A complete fix needs:

• A per-vector metadata shape across the SDK and N-API.
• Metadata segment persistence and reload.
• Aligned filter types, including valueType.
• Either metadata-bearing search results or getMetadata(id).
• Close/reopen tests, including vectors with unequal metadata-field counts.

Start with npm/packages/rvf/src/backend.ts and reproduce the public SDK and native N-API cases described in the issue. Trace the native SearchResult, MetadataStore, metadata segment persistence, and filter parsing, then add close/reopen coverage including unequal metadata-field counts. Done means metadata is not silently dropped, filters remain effective after reopening, and callers can retrieve metadata or receive metadata-bearing results.