Add production Hybrid OPFS PWA integration

[npiesco]

Summary

• finish the Hybrid OPFS + IndexedDB backend, recovery path, benchmark coverage, and multi-tab behavior
• add a production Next.js PWA with SharedWorker coordination, elected dedicated-worker database ownership, complete offline precaching, and local WASM packaging
• use the proven Onyx persistence and Playwright methodology as a behavioral reference without adding an Onyx runtime dependency
• repair the UniFFI import path and async database locking, then document the complete PWA and mobile validation state
• remediate the PWA dependency graph through the configured Microsoft CFS feed

Why

The browser integration needed one authoritative worker-owned Hybrid database runtime across tabs, durable OPFS recovery, and production-mode offline validation. During full regression validation, mobile import/export also exposed unqualified SQLite schema operations that could drop the attached import table when restoring into an empty destination; this PR qualifies destination operations against main and uses async-aware per-database locks.

Impact

Browser consumers gain production Hybrid OPFS persistence, coordinated cross-tab runtime handoff, offline reload, explicit backend benchmarking, and CI coverage. Native storage behavior is unchanged. The mobile UniFFI surface retains filesystem persistence and now passes the complete locked host integration matrix, including all import/export cases.

Validation

• production PWA Playwright suite: 3/3 passed in Chrome
• focused root Hybrid/OPFS recovery and benchmark Playwright suites passed
• explicit IndexedDB/Hybrid benchmark sweep passed
• npm audit --json: 0 vulnerabilities through the configured Microsoft CFS feed
• root cargo test, formatting, warning-free clippy, and release build passed
• mobile UniFFI host suite: 67/67 passed
• mobile focused real import/export suite: 9/9 passed
• mobile formatting, warning-free clippy, and locked release build passed

Detailed implementation provenance and per-section npiesco citations for both Onyx references and AbsurderSQL code are recorded in docs/HYBRID_OPFS_PLAN.md.