Add granular Apple Swift build primitives

You can now declare Apple Swift targets directly in fabrik.toml using four new primitives: apple.swift_library, apple.static_framework, apple.dynamic_framework, and apple.macos_command_line_application. A swift_library expands into separate, cacheable compile and archive actions, and dependencies resolve automatically for compilation modules or linking roots. Dependencies inside the same file can be written by target name (e.g., Greeter), and ./ and ../ references resolve relative to the declaring fabrik.toml file, making multi-target Apple projects easier to model.