fix(testing): stabilize TSAN coverage, harden daemon shutdown, and speed up KG/storage paths (#53)
* perf(search, metadata): add KG write buffer, score cache, adaptive budgets
* perf(indexing): wire KGWriteBuffer into indexing service
Converts per-document addEdgesUnique calls into batched flush via
KGWriteBuffer. 500-doc ingest: 500 SQL round-trips → 1 batch.
Verified: 14.2× edge insert gap (14.8K→195K edges/s) in kg_edge bench.
Tests: 10/10 Catch2 pass (105 assertions).
* perf(storage): add fsync durability, parallel batch, read integrity
* test(storage): add stress, crash-sim, cold-cache, batch benchmarks
* fix: CI optimizations and work coordinator shutdown fix
* fix(testing): stabilize TSAN coverage gate
* fix: harden KG flush, score cache, and benches
- keep KG buffers intact when batch commit fails
- count flushed edges per batch instead of lifetime totals
- guard the Simeon score cache and clear it on rebuild
- fall back to fsync when F_FULLFSYNC fails on macOS
- remove interactive sudo from cold-cache benchmarks
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