test: 130 edge case tests + fix NaN/Infinity bug in cosine_similarity
Edge cases found 2 real bugs:
- cosine_similarity(NaN, ...) returned NaN instead of 0.0
- cosine_similarity(Infinity, ...) returned NaN instead of 0.0
Fix: added is_finite() guards on denom and raw ratio.
New edge case tests by module:
- vector.rs (18): NaN, Infinity, negative vectors, opposite vectors clamped,
high-dimensional (1536), single element, both-zero, non-aligned bytes,
3-byte input, special float values, NaN roundtrip, limit=0, zero weights,
negative BM25 scores, duplicate IDs, large normalization, single item
- embeddings.rs (8): noop embed_one error, empty batch, multiple texts,
empty/unknown provider, custom empty URL, no API key, trailing slash, dims
- chunker.rs (11): headings-only, deeply nested ####, long single line,
whitespace-only, max_tokens=0, max_tokens=1, unicode/emoji, FTS5 special
chars, multiple blank lines, trailing heading, no content loss
- sqlite.rs (23): FTS5 quotes/asterisks/parens, SQL injection, empty
content/key, 100KB content, unicode+emoji, newlines+tabs, single char
query, limit=0/1, key matching, unicode query, schema idempotency,
triple open, ghost results after forget, forget+re-store cycle,
reindex empty/twice, content_hash empty/unicode/long, category
roundtrip with spaces/empty, list custom category, list empty DB
869 tests passing, 0 clippy warnings, cargo-deny clean
ce4f36a3ab