7 commits across 3 TDD tasks (RED + GREEN per task) + .gitkeep cleanup;
36 Vitest tests across 7 test files green; npm run build clean under
TypeScript strict; all 6 CORE requirements (CORE-04 through CORE-09)
covered by at least one assertion.
Key structural decision documented in SUMMARY: SaveDB is a single
common-contract interface, not a union of IDBPDatabase | LocalStorageDBAdapter.
The union shape failed TypeScript-strict at the build gate; the interface
refactor isolates the type-system cast to one location at openSaveDB().
