Document IL2125 and IL3058 transitive reference compatibility warnings

[Copilot]

Summary

Documents new analyzer warnings IL2125 and IL3058 introduced in dotnet/runtime#118180 for verifying transitive dependency compatibility with trimming and Native AOT.

New warning documentation:

• IL2125: Referenced assembly is not annotated for trim compatibility - emitted when VerifyReferenceTrimCompatibility=true and a referenced assembly lacks IsTrimmable metadata
• IL3058: Referenced assembly is not annotated for AOT compatibility - emitted when VerifyReferenceAotCompatibility=true and a referenced assembly lacks IsAotCompatible metadata

Updated conceptual documentation:

• Added VerifyReferenceTrimCompatibility property to trim preparation guide
• Added VerifyReferenceAotCompatibility property to Native AOT overview
• Added note that IsAotCompatible metadata was introduced in .NET 10

Documentation approach:

• Uses consistent terminology: "annotated for trim/AOT compatibility" throughout
• Provides two options to fix violations: update the library or disable verification
• Does not suggest warning suppression (these warnings cannot be suppressed at source location)
• Includes ai-usage: ai-assisted disclosure in frontmatter per .NET documentation guidelines
• Displays warning messages in separate blocks rather than inline comments, since these are compilation-level warnings that don't point to specific source lines
• Documents recommended ways to enable the warnings: PublishTrimmed/IsTrimmable for trim warnings, and PublishAot/IsAotCompatible for AOT warnings

Both properties are opt-in, allowing library authors to enforce that all dependencies explicitly declare trim/AOT compatibility:

<PropertyGroup>
  <IsTrimmable>true</IsTrimmable>
  <VerifyReferenceTrimCompatibility>true</VerifyReferenceTrimCompatibility>
</PropertyGroup>

Original prompt

Clone https://github.com/dotnet/runtime/pull/118180 and inspect the changes. Then write documentation for the new feature.

---

💡 You can make Copilot smarter by setting up custom instructions, customizing its development environment and configuring Model Context Protocol (MCP) servers. Learn more Copilot coding agent tips in the docs.

---

Internal previews

📄 File	🔗 Preview link
docs/core/deploying/native-aot/index.md	Native AOT deployment
docs/core/deploying/native-aot/warnings/il3058.md	"IL3058: Referenced assembly is not annotated for AOT compatibility"
docs/core/deploying/trimming/prepare-libraries-for-trimming.md	Prepare .NET libraries for trimming
docs/core/deploying/trimming/trim-warnings/il2125.md	IL2125: Referenced assembly is not annotated for trim compatibility