fix: avoid duplicate type modifier in exports

[privatenumber]

Summary

• Fixes a rewrite bug where namespace exports like export { type T } became invalid export type { type T }.
• When grouping type-only exports under export type { ... }, the fixer now prints only the export binding, e.g. T or U as V.
• Adds a regression fixture for plain and aliased namespace type exports.

Test

• npm test -- namespace-type-export-specifier
• npm test

[Swatinem]

thanks.

I haven’t forgotten about your other PR. Its quite large and I haven’t found enough motivation yet to look at it thoroughly.