feat: benchmark filtered vector search

[zhangzhenghao]

Summary

• add VectorDBBench-compatible integer-range and label-equality filtered vector cases
• load filtered ground truth and scalar labels, build scalar inverted indexes, and apply filters in xvec/zvec queries
• include filter settings in reports, reject unsupported sqlite-vec workloads, and document usage

Testing

• CGO_ENABLED=0 ZVEC_LIBRARY_PATH=/home/openclaw/.cache/zvec-libs-test/linux_amd64/libzvec_c_api.so go test ./cmd/vector-db-bench -count=1
• CGO_ENABLED=0 ZVEC_LIBRARY_PATH=/home/openclaw/.cache/zvec-libs-test/linux_amd64/libzvec_c_api.so go test ./... -count=1
• CGO_ENABLED=0 ZVEC_LIBRARY_PATH=/home/openclaw/.cache/zvec-libs-test/linux_amd64/libzvec_c_api.so go vet ./...
• built the benchmark and verified integer-filter and label-filter --dry-run configurations

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[codecov]

Codecov Report

❌ Patch coverage is 89.55224% with 14 lines in your changes missing coverage. Please review.
✅ Project coverage is 81.42%. Comparing base (835305c) to head (85cf434).

Files with missing lines	Patch %	Lines
cmd/vector-db-bench/dataset.go	82.92%	7 Missing ⚠️
cmd/vector-db-bench/config.go	92.53%	5 Missing ⚠️
cmd/vector-db-bench/benchmark.go	91.66%	2 Missing ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##             main      #95      +/-   ##
==========================================
+ Coverage   81.40%   81.42%   +0.02%     
==========================================
  Files         150      150              
  Lines       30551    30672     +121     
==========================================
+ Hits        24870    24975     +105     
- Misses       5679     5695      +16     
  Partials        2        2              

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