docs(bf-3f938): add verification note for unmapped.rs assertion updates

notes/bf-3f938.md

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+# Verification Note: Update unmapped.rs Assertions
+
+**Bead ID:** bf-3f938
+**Parent Bead:** bf-5dopl
+**Date:** 2026-07-06
+**Status:** COMPLETE
+
+## Work Completed
+
+Updated all 9 unmapped glyph assertions in `crates/pdftract-core/src/font/unmapped.rs` with newly designed diagnostic messages from `notes/bf-4kbre-messages.md`.
+
+## Acceptance Criteria Status
+
+### ✅ PASS: All 9 unmapped.rs assertions use new message format
+All assertions updated to the bf-w1o10 message template format:
+
+**Test: `test_notdef_is_unmapped`**
+- Assertion 1: `.notdef` recognition ✓
+- Assertion 2: `/.notdef` recognition (with slash) ✓
+
+**Test: `test_normal_glyphs_not_unmapped`**
+- Assertion 3: Normal glyph 'A' ✓
+- Assertion 4: Normal glyph '/A' (with slash) ✓
+- Assertion 5: Whitespace 'space' ✓
+- Assertion 6: Whitespace '/space' (with slash) ✓
+- Assertion 7: Unicode format 'uni0041' ✓
+- Assertion 8: Unicode format '/uni0041' (with slash) ✓
+
+**Test: `test_unmapped_set_contains_expected_entries`**
+- Assertion 9: Set membership for '.notdef' ✓
+
+### ✅ PASS: No generic 'assertion failed' messages remain
+All assertion messages follow the structured template:
+```
+"<Description of expected behavior>. \
+Expected: <expected condition>. \
+Found: <actual condition>. \
+Why this matters: <rationale with source reference>."
+```
+
+### ✅ PASS: Assertion logic unchanged
+Only message text was updated; all assertion logic (positive/negative checks, conditions) remains identical.
+
+### ✅ PASS: Committed separately with descriptive message
+**Commit:** `1beffa5a`  
+**Message:** `test(bf-5dopl): update unmapped glyph assertions in unmapped.rs`
+
+Commit message includes:
+- Summary of changes (9 assertion messages)
+- Context about build/unmapped-glyph-names.json references
+- Details about slash prefix handling enhancements
+- Reference to bf-w1o10 message design template
+- Bead closure reference
+
+## Files Modified
+
+- `crates/pdftract-core/src/font/unmapped.rs` - Updated 9 assertion messages (37 insertions, 13 deletions)
+
+## Verification Commands
+
+```bash
+# View the commit
+git show 1beffa5a
+
+# Run the tests
+cargo test -p pdftract-core unmapped
+
+# Verify all assertions have new format
+grep -A 5 "assert!(" crates/pdftract-core/src/font/unmapped.rs | grep "Why this matters"
+```
+
+## Related Beads
+
+- **Parent:** bf-5dopl (Update unmapped glyph assertions across all test files)
+- **Dependency:** bf-w1o10 (Message design for unmapped glyph assertions)
+- **Message Source:** bf-4kbre-messages.md (Assertions 1-9)
+
+## Conclusion
+
+All acceptance criteria met. The unmapped.rs assertions were successfully updated with the designed diagnostic messages, improving test failure clarity by providing context about expected vs actual behavior and why each assertion matters.