Function parse_shell_commands 

pub fn parse_shell_commands(script: &str) -> Result<Vec<Vec<String>>, String>

Parses a shell script into individual commands using tree-sitter bash grammar

Example

Input:  "git status && cargo check"
Output: Ok([["git", "status"], ["cargo", "check"]])

Fallback

If tree-sitter parsing fails, falls back to simple tokenization