Function preprocess_semicolons 

pub fn preprocess_semicolons(source: &str) -> String

Automatic semicolon insertion preprocessor.

Resolves newline ambiguities where [...] or (...) on a new line could be parsed as index access or function call (Pest’s greedy postfix matching).

Inserts ; at the end of lines where:

1. The line ends with a statement-ending token (identifier char, ), ], }, ")
2. The next non-empty line starts with [ or (

This mirrors Go’s automatic semicolon insertion strategy.