Friendly error when non-matching SDK is used

[kzu]

Since we are building with latest&greatest .NET to get the extension class syntax, consumers need to use a matching SDK in order for that to work.

Provide a compile-time error instead of the inscrutable alternative (unsupported language feature or what-not).

This will turn off itself when we ship with a stable SDK.

[Copilot]

Pull Request Overview

This PR implements a compile-time check to ensure consumers use a matching SDK version when the package is built with a preview .NET SDK. The change prevents cryptic compilation errors by providing a clear error message when an incompatible SDK is detected.

Key changes:

• Adds MSBuild targets to validate SDK version compatibility at build time
• Dynamically updates SDK version information during package creation
• Provides user-friendly error messaging for SDK mismatches

Reviewed Changes

Copilot reviewed 2 out of 2 changed files in this pull request and generated 2 comments.

File	Description
src/AI/Devlooped.Extensions.AI.targets	Adds build-time validation target with SDK version check and error message
src/AI/AI.csproj	Implements dynamic update of SDK version properties during packaging

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[Copilot]

[nitpick] The condition logic could be clearer by separating the two error cases. Consider using separate Error elements for when SDK is not preview vs when versions don't match, as these are different problems requiring different solutions.

Suggested change

	<ErrorCondition="'$(_NETCoreSdkIsPreview)' == 'false' or '$(NETCoreSdkVersion)' != '$(BuiltSdkPreviewVersion)'"Text="This version was built with a preview SDK and requires a matching one. Please install SDK version $(BuiltSdkPreviewVersion) or update to a newer package version." />
	<ErrorCondition="'$(_NETCoreSdkIsPreview)' == 'false'"Text="This version was built with a preview SDK. Please use a preview .NET SDK (version $(BuiltSdkPreviewVersion) or newer)." />
	<ErrorCondition="'$(_NETCoreSdkIsPreview)' == 'true' and '$(NETCoreSdkVersion)' != '$(BuiltSdkPreviewVersion)'"Text="This version was built with .NET SDK version $(BuiltSdkPreviewVersion). Please install and use this SDK version, or update to a newer package version." />

[kzu]

🧪 Details on Ubuntu 24.04.2 LTS

from dotnet-retest v0.7.2 on .NET 9.0.8 with 💜 by @devlooped