Fix tuist cache failure for pure-Swift SPM packages promoted to frameworks

Resolved a build failure when using tuist cache with pure-Swift SwiftPM packages that are promoted to .framework via PackageSettings.productTypes. Under Xcode 26, the cache build could fail with a <Module>-Swift.h not found error on single-arch simulator builds. Tuist now generates a minimal modulemap for Swift-only SwiftPM framework products and disables Xcode’s synthesized modulemap, so the dependency scanner no longer references a header that has not yet been emitted.