Shen S42 compiled Python backend (experimental)

This branch mirrors the Common Lisp port architecture:
  KLambda -> Python AST -> Python compile() -> exec()

It deliberately does NOT install Shen/Lib yet.  The S42 KLambda kernel is
compiled and loaded, and dynamically loaded Shen definitions are compiled
through eval-kl as well.

Windows:
  1. Double-click install.bat
  2. In a new Command Prompt type: shen-compiled

The known-good interpreted port remains separate and untouched.

0.4.1 path fix: relative *home-directory* values are resolved against the Shen launch directory. install.bat no longer auto-starts Shen from the installer directory.
