Function fetch_first_match_for_query 

pub async fn fetch_first_match_for_query(q: String) -> Option<PackageItem>

What: Resolve a free-form query string to a best-effort matching package.

Inputs:

• q: Query string to resolve

Output:

• Some(PackageItem) per the priority rules below; None if nothing usable is found.

Details (selection priority):

1. Exact-name match from the official index;
2. Exact-name match from AUR;
3. First official result;
4. Otherwise, first AUR result.

Performs network I/O for AUR; tolerates errors.