fix(web): track transaction completion and connection lifetime - #1334

Summary

Propagate open/transaction failures through caller promises, wait for deletion commit, close blocking connections and discard terminated connections.

Compatibility / observable behavior

removeMany now rejects when its transaction aborts. Version-change requests close the old connection; later calls reopen (and reject normally if another client upgraded beyond version 1). Blocked opens wait through IndexedDB instead of throwing from an unrelated event callback.

Related to #1331. This is a focused part of a source review; it does not claim the entire repository is bug-free.

Test Plan

• Real idb 8.0.3 with fake-indexeddb: failed-open retry, get/put/delete aborts, rollback, empty batches, normal CRUD, forced termination and external database deletion. Baseline has unhandled rejections, resolves an aborted deletion, reuses a closed database and prevents external deletion; fixed handles all cases.
• Upstream yarn build:js, yarn test:ts (6 tasks), yarn test:lint (6 tasks), yarn test:format and git diff --check pass on the combined review checkout.
• No checked-in test/spec files changed. Reproductions were isolated and used synthetic data, not production/user storage.
• The combined 3.1.1 backport passes consumer immutable install/lint, both products' Android Debug and iOS Simulator Debug builds, four production Metro bundles, 13 web targets and four browser-extension targets. Published native framework binaries are unchanged. React Doctor: 100/100.
• Shared-storage testAndroidHostTest, macosArm64Test and iosSimulatorArm64Test pass with Java 21. The first Android run used Java 17 and failed Robolectric's SDK 36/JDK check; rerunning with the project's documented JDK fixed the environment failure without a source workaround.
• Windows/WinRT runtime, signed releases and physical-device behavior have not been verified locally.