Function find_references 

pub async fn find_references(
    ctx: &RefactoringContext,
    symbol_name: &str,
    def_file: &str,
) -> References

Find all cross-file references to a symbol (callers + importers).

Returns empty references if no index is available.

Each reference is tagged with a confidence field:

• "resolved" — backed by ModuleResolver import resolution (accurate)
• "heuristic" — found via import-name matching without full resolution (may have false positives)