DocC builds work for SwiftPM packages with cross-module public imports

Generated Tuist projects can now produce DocC builds for SwiftPM packages whose public headers import another module from the same package, even when that import is not declared as a target dependency in Package.swift (the Firebase pattern). Tuist derives the missing target dependency from concrete #import/#include references in public headers, with cycle and same-target guards, and copies dependency framework module maps to the canonical Modules/module.modulemap path so Clang ExtractAPI can resolve them.