fix(api-extractor): preserve export keyword for namespace re-exports

[ItsChrisHickman]

Summary

Fixes #5516

When a namespace contains export { Foo, Bar }; re-export declarations, api-extractor was incorrectly stripping the export keyword, producing { Foo, Bar, }; which is syntactically invalid TypeScript.

Input:

export declare namespace SDK {
  export { Color, Vector3 };
}

Before (invalid):

export declare namespace SDK {
        { Color, Vector3, };
}

After (valid):

export declare namespace SDK {
        export { Color, Vector3, };
}

Details

The issue is in DtsRollupGenerator.ts and ApiReportGenerator.ts. Both files unconditionally skip all ExportKeyword tokens (lines ~272-276), then re-add them for declaration types (interface, class, enum, namespace, function, type). However, ExportDeclaration nodes (like export { Foo }) were not handled, so the export keyword was stripped but never restored.

The fix checks if an ExportKeyword is part of an ExportDeclaration that is inside a ModuleBlock (namespace body), and if so, preserves it.

How it was tested

1. Created a minimal reproduction case with a namespace containing export { } declarations
2. Verified that tsc produces valid output
3. Verified that api-extractor (before fix) produces invalid output (TS1109)
4. Applied fix and verified api-extractor now produces valid output

[ItsChrisHickman]

@microsoft-github-policy-service agree