Add [Description] to DataContent.Uri

[stephentoub]

So that if a DataContent has schema generated for it, it's obvious in the schema that the "uri" is specifically a data URI.

Microsoft Reviewers: Open in CodeFlow

[Copilot]

Pull Request Overview

This PR adds a description attribute to the DataContent.Uri property so its generated JSON schema clearly indicates it’s a data URI, and introduces a test to verify that description appears in the schema.

• Added [Description("A data URI representing the content.")] to DataContent.Uri.
• Added a new test GenerateSchema_ContainsDataUriDescription to assert the schema includes the phrase "data URI".

Reviewed Changes

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

File	Description
test/Libraries/Microsoft.Extensions.AI.Abstractions.Tests/Contents/DataContentTests.cs	New test to check the schema text contains the data URI description
src/Libraries/Microsoft.Extensions.AI.Abstractions/Contents/DataContent.cs	Added using System.ComponentModel and [Description(...)] on Uri property

Comments suppressed due to low confidence (1)

src/Libraries/Microsoft.Extensions.AI.Abstractions/Contents/DataContent.cs:146

• The DescriptionAttribute is only applied when NET is defined, so on other target frameworks the JSON schema won't include the description. If schema generation supports multiple targets, consider removing the conditional so the attribute is always applied.

#if NET

[stephentoub]

@eiriktsarpalis, any concerns?

[eiriktsarpalis]

@eiriktsarpalis, any concerns?

No huge concerns, from my perspective though I'd rather have the ns2.0 build take the extra dependency as opposed it not exposing the same metadata.