Tests 1-5 (assertions 10-41) in crates/pdftract-core/src/font/encoding.rs
already contain the new diagnostic message format from notes/bf-4kbre-messages.md.
Test 6 (test_differences_overlay_with_slashed_names) does not exist in the file.
All existing tests pass with the updated messages.
Verification: notes/bf-4dagm.md
