[Repo Assist] eng: enable PackageValidationBaselineVersion=0.4.0 with suppression for known breaking changes

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Activates binary compatibility checking against the last published release (v0.4.0) by uncommenting PackageValidationBaselineVersion in the project file. EnablePackageValidation was already enabled (added in PR #315), but without a baseline version only structural package validation ran — no cross-version binary compatibility check.

What this enables

With PackageValidationBaselineVersion=0.4.0, every dotnet build and CI run now automatically verifies that all public APIs present in FSharp.Control.TaskSeq 0.4.0 are still present in the current version with compatible signatures. Any future inadvertent breaking change will produce a build error rather than being silently shipped.

What it found

Running the check immediately revealed 3 existing API breaks between 0.4.0 and the current 0.6.0-dev. All three are in compiler-internal F# CE infrastructure — technically public members but not intended for direct user consumption:

Member	Notes
FSharp.Control.LowPriority.TaskSeqBuilder.Bind<...>	Internal CE Bind overload
FSharp.Control.LowPriority.TaskSeqBuilder.Bind$W<...>	F# witness-passing variant (compiler-generated)
FSharp.Control.TaskExtensions.TaskBuilder.For(T,TOverall)	for x in IAsyncEnumerable overload for task {}

These are suppressed in the new CompatibilitySuppressions.xml file (standard .NET SDK mechanism). The suppression file format is documented at (learn.microsoft.com/redacted)

Note for maintainers: while these members are not part of the documented public API, technically they represent binary breaks for any assembly that compiled against 0.4.0 and called these members. In practice this is extremely unlikely (they require direct use of F# compiler internals). The suppressions acknowledge this intentional deviation.

Files changed

• FSharp.Control.TaskSeq.fsproj: uncomment PackageValidationBaselineVersion
• CompatibilitySuppressions.xml: suppress 3 known compiler-internal breaking changes (new file)
• release-notes.txt: document engineering change

Test Status

✅ Build (Release): succeeded, 0 warnings, 0 errors
✅ Package validation: passes with suppression file
✅ No code changes — library logic is unmodified

🤖 Generated by Repo Assist · Task 4: Engineering Investments

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