Fix getStores endpointURL under production minification

[sirdeggen]

Summary

• WalletStorageManager.getStoreEndpointURL used constructor.name === 'StorageClient', which fails after Vite/esbuild/webpack minify renames the class.
• Remote backups still synced (walks _backups), but clients that match stores by URL (e.g. bsv-desktop Make Primary) saw endpointURL: undefined and failed with "No storage provider matching …".
• Resolve the URL by duck-typing provider.endpointUrl instead.

Changes

• WalletStorageManager.getStoreEndpointURL: duck-type endpointUrl; document why constructor.name is unsafe
• Unit tests for normal, minified class name, local/empty, and getStores() exposure
• CHANGELOG note under unreleased

Test plan

• pnpm exec jest --runTestsByPath test/storage/getStoreEndpointURL.test.ts (5 passed)
• After publish/link into bsv-desktop: add remote backup, Sync works, Make Primary on https://store-us-1.bsvb.tech succeeds

[sonarqubecloud]

Quality Gate passed

Issues
0 New issues
0 Accepted issues

Measures
0 Security Hotspots
0.0% Coverage on New Code
0.0% Duplication on New Code

See analysis details on SonarQube Cloud

[ty-everett]

The implementation itself looks sound: duck-typing the existing endpointUrl property avoids the minified-class-name failure and covers both remote storage client variants. On this exact head I verified the focused suite (5/5), wallet-toolbox typecheck, package lint, and git diff --check locally. SonarCloud is also green with zero new findings and zero security hotspots.

There are still merge blockers that need an updated head:

• This branch no longer merges cleanly with main; please rebase and resolve the wallet-toolbox CHANGELOG conflict while preserving both entries.
• The required CI merge gate is red. Build, lint, and policy failed in docs:examples with unresolved workspace packages, the downstream test/coverage jobs were skipped, and Mutation quality plus build-and-test (24.x) consequently failed. Please rerun CI after the rebase and ensure the full required matrix—not only Sonar and the focused test—is green.

Once the branch is current and the complete CI/merge gate passes, I see no code-level blocker in this patch.