externum Files

Bash target is now full

def/fn compile to real bash functions:

• positional params bound with local (recursion-safe — fact(6) → 720)
• default params: def greet(name, suffix = "!") → local suffix="${2:-!}"
• return <expr> → printf '%s\n' + return 0, captured via $( f args )
• string concatenation (s + "!") renders as one double-quoted word — in expressions, return and print
• bare calls to value-returning functions discard the result (> /dev/null), matching the Python target; compile-time warning when a function both prints and returns

Also fixes an f-string gotcha in the codegen (${i:-d} parsed as format spec).

379 tests. PyPI: pip install externum==4.2.1