Fourth Release: Python API and Package

• Exposing a Python runtime and API, used with "import joyfl.api as J".
• New error types that are Joy specific so they can easily be caught.
• Rework the architecture to break up the single-file script into components.
• Support for "factory" terms that can inject Python object into quotations at comp-time.
• If operators contain a dot namespace, the code auto-imports from corresponding function in libs/_{ns}.py.
• Named-tuple for Stack object, for efficiency, easier print/debug, and better safety.
• Allow for JOY_PATH envvar to load extension modules and the standard library.
• Using uv for build testing, packaging and publishing.
• Improved error handling showing Joy source more consistently.
• Fix for win32 support when using the repl, previously broken.
• Support fraction types when you use the unicode ⁄ separator for numerator and denominator.
• Python-side operators use standard type annotations for ease-of-use, correctness.