Function batch_diff_versions 

pub fn batch_diff_versions(
    base: &str,
    patches_json: &str,
    base_version: u32,
    version_numbers_json: &str,
) -> Result<String, String>

Compare multiple versions against a base version in a single call.

version_numbers is a JSON array of version numbers to compare: [1, 3, 5, 8]. Each is reconstructed from the patch chain and diffed against base_version. Returns a JSON array of diff results.

This avoids N separate WASM calls and parses the patches JSON once.