Verification coverage

• Automated core tests cover comments and metadata preservation, record/map fields, nested references, rename, delete guards, creation, invalid YAML, null-type mistakes, and other edit boundaries.
• A Chromium webview harness exercises the actual UI and core edit model: context-menu creation, inline Enter/blur/Escape, enum-list CRUD, automatic reference arrows, actual mouse-drawn wires with preview and cancellation at two zoom levels, card dragging, deletion guards, search, and a mocked document undo/redo bridge.
• A separate host API test exercises version rejection, failed-edit handling, text edit range, save-time ordering (including clean files), invalid-YAML and unrelated-file handling, event refresh, and disposal with API test doubles.
• Serialization regression tests cover forward references, transitive types, inheritance, specialization, imports, namespaces, comments, aliases, recursive groups, block-style output, and stable repeated saves.
• The browser harness verifies selection, card positions, and subsequent field edits after dependency-ordered Save, checkbox toggles, wiring with modifiers, and scalar/enum/array/record/mapping default forms.

These harnesses do not launch an actual VS Code Extension Development Host. A real-host installation smoke test remains necessary before release to users.