feat: release memory write-ahead VFS 0.2.0

[whygee-dev]

Summary

• upstream the generic shared-memory runtime improvements, including deferred writes, attached-database serialization, lifecycle recovery, and expanded diagnostics
• fail closed by quarantining attached databases when their rollback-journal owner terminates mid-transaction
• publish a reproducible PowerSync MemoryVFS benchmark with explicit worker, connection-pool, and aggregate-cache topology
• add release CI, third-party provenance, a constrained wa-sqlite peer range, and package validation

Benchmark

In the both-workers comparison, the 3-connection Memory Write-Ahead VFS pool recorded 49.0% lower median concurrent-read latency, 47.6% lower median mixed-read latency, and 75.2% lower median mixed-workload write-completion latency than PowerSync MemoryVFS with one connection. The published artifacts disclose aggregate cache ceilings for every arm; RSS was not measured, so the 3-connection recommendation is throughput-focused rather than memory-balanced.

Validation

• pnpm prepublishOnly (format, types, benchmark publisher, 27 browser tests, build)
• pnpm test:stress (540/540)
• three full benchmark configurations and sanitizer validation
• pnpm audit --prod
• npm pack plus fresh consumer install/import