fix: correct Image component descriptor handling for fluid images

[z0n]

WHY are these changes introduced?

The Image component can produce 1x/2x/3x density descriptors for fluid (responsive) images when the source image dimensions are small enough that the srcset ladder is filtered down to exactly 3 entries. In that case the sizes attribute is silently ignored and the browser always picks images by DPR instead of container size, causing blurry images on low-DPR screens.

WHAT is this pull request doing?

generateSrcSet determined descriptor type (x vs w) by checking sizesArray.length === 3, under the assumption that only fixed-width images produce exactly 3 entries. That assumption breaks when source-dimension filtering reduces a fluid image's srcset to exactly 3 entries (e.g. a 600px-wide image with default srcSetOptions produces [200, 400, 600]).

The fix adds an explicit fixed boolean parameter to generateSrcSet (defaulting to false) and uses it instead of the length heuristic. FixedWidthImage passes true; FluidImage uses the default.

HOW to test your changes?

Render a fluid Image with a small source image (e.g. data={{ url: '...', width: 600, height: 600 }}) and a sizes prop. Before this fix, the srcset attribute contains 1x/2x/3x descriptors and sizes is ignored. After this fix, srcset contains 200w/400w/600w descriptors and sizes is respected.

The new regression test in Image.test.tsx covers this case directly.

Checklist

• I've read the Contributing Guidelines
• I've considered possible cross-platform impacts (Mac, Linux, Windows)
• I've added a changeset if this PR contains user-facing or functional changes. Test changes or internal-only config changes do not require a changeset.
• I've added tests to cover my changes
• I've added or updated the documentation

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[fredericoo]

thanks for your contribution! a few comments but overall this is very neat

[z0n]

thanks for your contribution! a few comments but overall this is very neat

Thanks for the comments, I made the usage a bit more explicit and added the missing test assertions 🙂