Extend cross-platform tests to verify Platform.name returns one of seven known
OS strings and assert Process.version splits into exactly three numeric
components, while fixing missing trailing newline in isPosix test file.
Rename the "process" module to "os" across all source files, documentation, tests, and build configuration. Add a new Platform class to the os module with static methods `name` (returns OS string like "Windows", "Linux", "OS X", "iOS", "Unix", "POSIX", or "Unknown") and `isPosix` (returns bool indicating POSIX compliance). Update all import paths from "process" to "os" in test files and module registrations. Move process.c/h to os.c/h, rename processSetArguments to osSetArguments, and regenerate the os.wren.inc bytecode source. Add documentation pages for the os module and Platform class.
