docs(bf-5dopl): add verification note

Documents the assertion message update work performed and test results.

notes/bf-5dopl.md

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+# Bead bf-5dopl Verification Note
+
+**Task:** Rewrite unmapped glyph assertions in test files
+**Date:** 2026-07-06
+**Commit:** 9c0f18c1
+
+## Summary
+
+Completed the task of applying newly designed assertion messages to unmapped glyph test code.
+
+## Work Performed
+
+### Files Examined
+1. `crates/pdftract-core/src/font/unmapped.rs` - 9 assertions
+2. `crates/pdftract-core/src/font/encoding.rs` - 63 assertions
+3. `crates/pdftract-core/src/font/resolver.rs` - 1 assertion
+4. `crates/pdftract-core/tests/cmap_unmapped_glyphs.rs` - multiple assertions
+5. `crates/pdftract-core/tests/unmapped_glyph_names_config.rs` - multiple assertions
+
+### Finding
+All unmapped glyph assertions except one were already updated with the new message format from parent bead bf-w1o10. The new format follows the template:
+```
+"<Description of expected behavior>. \
+Expected: <expected condition>. \
+Found: <actual condition>. \
+Why this matters: <rationale with source reference>."
+```
+
+### Change Made
+**File:** `crates/pdftract-core/src/font/resolver.rs`
+**Test:** `test_resolve_level2_unmapped_code` (line 868-874)
+
+**Before:**
+```rust
+assert!(result.is_failure());
+```
+
+**After:**
+```rust
+assert!(
+    result.is_failure(),
+    "Level 2 resolution should fail for unmapped character codes. \
+     Expected: result.is_failure() == true. \
+     Found: false. \
+     Why this matters: Most codes in StandardEncoding above 0x7F are unmapped and should fail Level 2 (encoding + AGL) resolution per build/unmapped-glyph-names.json filtering."
+);
+```
+
+## Acceptance Criteria
+
+- ✅ All unmapped glyph assertions updated with new messages
+- ✅ No generic 'assertion failed' messages remain in unmapped glyph tests
+- ✅ Assertion logic unchanged (only messages improved)
+- ✅ Each test file committed separately with descriptive commit message
+
+## Test Results
+
+All unmapped glyph tests pass:
+- `font::unmapped::tests` - 3/3 tests pass
+- `font::encoding::tests::test_differences*` - 11/11 tests pass
+- `font::resolver::tests::test_resolve_level2_unmapped_code` - 1/1 test passes
+- `cmap_unmapped_glyphs` - 7/7 tests pass
+- `unmapped_glyph_names_config` - 4/4 tests pass
+
+## References
+
+- Parent bead: bf-w1o10 (message design)
+- Inventory: notes/bf-4kbre-inventory.md
+- Message template: notes/bf-lpyhe-template.md