Investigation findings:
- Tests 7-15 (assertions 45-72) do not exist in crates/pdftract-core/src/font/encoding.rs
- Current file has 1345 lines and 20 test functions
- Message design document references tests that would extend to line 1646
- Last existing test is test_unmapped_glyph_skip_behavior (lines 1255-1343)
Cannot complete task - referenced tests were never implemented.
If these tests are needed, they should be created as a separate task.
Refs: bf-mj6ea
