Function decode_scopes 

pub fn decode_scopes(
    input: &str,
    names: &[String],
    num_sources: usize,
) -> Result<ScopeInfo, ScopesError>

Decode a scopes string into structured scope information.

• input: the VLQ-encoded scopes string from the source map
• names: the names array from the source map (for resolving indices)
• num_sources: number of source files (length of sources array)