- Replace browser store non-null assertions with explicit initialization guards
- Use expectDefined for optional test resources and tool results
- Clean low-count non-null assertions in font, icon, snap, OKHCL, and visual tests
- Move tools.test.ts into focused registry, create, modify, read, and structure files
- Add shared tool test helpers for graph setup and tool lookup
- Preserve all 38 tool tests after the split
