fix: recognize Icon Composer .icon file type

[jsj]

Short description 📝

This change recognizes Xcode 26 Icon Composer .icon bundles during file-reference generation.

Solution 📦

Xcode maps the icon extension to folder.iconcomposer.icon.

XcodeProj did not contain this mapping. Thus, Tuist-generated projects created PBXFileReference entries without a lastKnownFileType value for AppIcon.icon.

Local Xcode inferred the file type. Xcode Cloud did not infer the file type. It treated the bundle as a plain folder.

As a result, actool received only Assets.xcassets. It did not find AppIcon.

This change adds the missing mapping to Xcode.filetype(extension:).

Implementation 👩‍💻👨‍💻

• This change maps .icon to folder.iconcomposer.icon.
• A regression test covers this mapping.
• swift test --filter XcodeTests passes.
• The affected project archives and exports an IPA locally with this mapping.
• Xcode Cloud now includes AppIcon.icon in the asset-compiler inputs.
• The project team handles a separate resource-ownership error in that repository.