fix browser opfs partial writes in ci

[KSemenenko]

Summary

• handle partial OPFS writes in the browser worker by draining each chunk in smaller blocks
• surface upload failures directly in the browser large-flow playgrounds instead of masking them as UnexpectedLength
• keep the 1 GiB browser verification unchanged while making the CI path reliable

Verification

• dotnet test Tests/ManagedCode.Storage.Tests/ManagedCode.Storage.Tests.csproj --configuration Release --filter "FullyQualifiedNameBrowserStorage_ServerHost_LargeFlow_ShouldPersistAcrossPages|FullyQualifiedNameBrowserStorage_WasmHost_LargeFlow_ShouldPersistAcrossPages"
• dotnet test Tests/ManagedCode.Storage.Tests/ManagedCode.Storage.Tests.csproj --configuration Release --filter "FullyQualifiedName~ManagedCode.Storage.Tests.Storages.Browser"
• dotnet test Tests/ManagedCode.Storage.Tests/ManagedCode.Storage.Tests.csproj --configuration Release
• dotnet format ManagedCode.Storage.slnx
• dotnet build ManagedCode.Storage.slnx

[Copilot]

Pull request overview

This PR improves reliability of browser OPFS (Origin Private File System) uploads—especially in CI—by handling partial FileSystemSyncAccessHandle.write() results and by surfacing real upload failures in the browser storage playground UIs instead of masking them as UnexpectedLength.

Changes:

• Add a write loop in the OPFS worker to drain each chunk via smaller block writes until fully written (tolerating short writes).
• Update both Wasm and Server storage playground pages to immediately report UploadAsync failures (and only use UnexpectedLength when the upload reports success but the deterministic stream did not fully drain).

Reviewed changes

Copilot reviewed 3 out of 3 changed files in this pull request and generated no comments.

File	Description
Storages/ManagedCode.Storage.Browser/wwwroot/browserStorage.worker.js	Implements block-based “write until complete” behavior to handle partial OPFS writes reliably.
Tests/ManagedCode.Storage.BrowserWasmHost/Pages/StoragePlayground.razor	Stops masking upload failures as UnexpectedLength; reports upload failure details directly.
Tests/ManagedCode.Storage.BrowserServerHost/Components/Pages/StoragePlayground.razor	Same failure-reporting behavior change as the Wasm playground.

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[codecov]

Codecov Report

❌ Patch coverage is 0% with 10 lines in your changes missing coverage. Please review.
✅ Project coverage is 48.55%. Comparing base (710b8bb) to head (6c9b6fe).
⚠️ Report is 4 commits behind head on main.

Files with missing lines	Patch %	Lines
...erverHost/Components/Pages/StoragePlayground.razor	0.00%	5 Missing ⚠️
...rage.BrowserWasmHost/Pages/StoragePlayground.razor	0.00%	5 Missing ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##             main     #117      +/-   ##
==========================================
- Coverage   57.27%   48.55%   -8.72%     
==========================================
  Files         133      153      +20     
  Lines        6540     7702    +1162     
  Branches      922     1029     +107     
==========================================
- Hits         3746     3740       -6     
- Misses       2362     3528    +1166     
- Partials      432      434       +2     

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