fix(idxdb-store): synchronize openDatabase to prevent worker reset race condition (#287)

[Lesnak1]

Summary

Fixes #287.

Initializing WebClient with the default useWorker: true starts WASM both on the main thread and in the web worker, calling openDatabase(storeName, clientVersion) concurrently against the same database.

When ensureClientVersion triggers a reset path (e.g. major/minor version mismatch or invalid semver), dexie.delete() emits a versionchange event that closes the peer connection. Whichever thread reaches delete() second deletes the freshly reopened database while settings reads/writes are in flight, rejecting with DatabaseClosedError and throwing Failed to initialize IdxdbStore.

Changes

• Web Locks Synchronization (crates/idxdb-store/src/ts/schema.ts):
  • Added acquireDbInitLock wrapping openDatabase using the standard Web Locks API (navigator.locks.request("miden-db-init:${name}", ...)).
  • Added an in-process promise queue fallback for non-browser/test environments without navigator.locks.
• Race-Free Store Resets:
  • The first worker/thread acquires the lock, performs the reset/nuke, persists the new version, and opens the DB.
  • The second instance waits for the lock, reads the updated getStoredClientVersion(), recognizes the version matches, and proceeds without closing or re-deleting the database.
• Compiled JS:
  • Synchronized crates/idxdb-store/src/js/schema.js.
• Testing:
  • Added test suite in crates/idxdb-store/src/ts/schema.test.ts asserting concurrent openDatabase calls during a major version reset complete cleanly without errors or dangling connections.
  • Added test asserting navigator.locks integration when present.

Verification

• All 12 test files (318 tests) in crates/idxdb-store pass cleanly (vitest run).
• Full React SDK test suite (62 files, 845 tests) passes.
• Pre-commit hooks (eslint --fix, prettier --write) passed.