chore(deps): update dependency polyfill to 9.1.0

[thomhurst]

This PR contains the following updates:

Package	Type	Update	Change
Polyfill	nuget	minor	9.0.3 -> 9.1.0

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Release Notes

SimonCropp/Polyfill (Polyfill)

v9.1.0

Compare Source

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[claude]

Claude finished @thomhurst's task —— View job

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PR Review: Polyfill Dependency Update

Review Summary: ⚠️ Critical Issue Found

This PR updates the Polyfill dependency from 9.0.3 to 9.1.0, but has a critical version mismatch that must be addressed.

Key Findings:

🚨 CRITICAL ISSUE:

• Directory.Packages.props is being updated to Polyfill 9.1.0 (line 62)
• TUnit.Core/TUnit.Core.targets still hardcodes version 9.0.3 (line 11: <_TUnitPolyfillVersion>9.0.3</_TUnitPolyfillVersion>)
• This creates inconsistent behavior for TUnit NuGet consumers vs internal builds

Code Quality & Security Analysis:

✅ POSITIVE:

• Polyfill is correctly configured as compile-time only (<PrivateAssets>all</PrivateAssets>)
• No runtime dependencies, reduces security attack surface
• Proper conditional inclusion for older target frameworks only
• Minor version update (9.0.3 → 9.1.0) should be backwards compatible

⚠️ CONCERNS:

• Version Synchronization: Consumer projects will get 9.0.3 while CI/internal builds use 9.1.0
• Testing Gap: The version mismatch means CI testing doesn't validate the same polyfill version consumers will use
• Potential Behavioral Differences: Any fixes or changes in 9.1.0 won't benefit NuGet consumers

Performance & Impact:

• Performance: ✅ No runtime impact (compile-time only polyfills)
• Compatibility: ✅ Minor version bump, should be safe
• Test Coverage: ✅ Limited polyfill usage (only custom ReplaceLineEndings extension found)

Recommended Actions:

1. REQUIRED: Update TUnit.Core/TUnit.Core.targets line 11 to use 9.1.0:

   <_TUnitPolyfillVersion>9.1.0</_TUnitPolyfillVersion>

2. RECOMMENDED: Consider centralizing the polyfill version in a shared location to prevent future mismatches

3. TESTING: Verify that consumer projects (especially targeting netstandard2.0/2.1) build correctly with the new version

Files Requiring Changes:

• TUnit.Core/TUnit.Core.targets:11 - Update hardcoded version to 9.1.0

This PR should NOT be merged until the version mismatch is resolved, as it will cause inconsistent behavior between CI and consumer builds.