Refocus workflow on TDD and reorganize stories

.story_kit/specs/tech/STACK.md

@@ -76,15 +76,18 @@ To support both Remote and Local models, the system implements a `ModelProvider`
 *   **Quality Gates:**
     *   `cargo clippy --all-targets --all-features` must show 0 errors, 0 warnings
     *   `cargo check` must succeed
-    *   `cargo test` must pass all tests
+    *   `cargo nextest run` must pass all tests
 
 ### TypeScript / React
 *   **Style:** Biome formatter (replaces Prettier/ESLint).
 *   **Linter:** Biome - Must pass with 0 errors, 0 warnings before merging.
 *   **Types:** Shared types with Rust (via `tauri-specta` or manual interface matching) are preferred to ensure type safety across the bridge.
+*   **Testing:** Vitest for unit/component tests; Playwright for end-to-end tests.
 *   **Quality Gates:**
     *   `npx @biomejs/biome check src/` must show 0 errors, 0 warnings
     *   `npm run build` must succeed
+    *   `npx vitest run` must pass
+    *   `npx playwright test` must pass
     *   No `any` types allowed (use proper types or `unknown`)
     *   React keys must use stable IDs, not array indices
     *   All buttons must have explicit `type` attribute
@@ -103,6 +106,8 @@ To support both Remote and Local models, the system implements a `ModelProvider`
     *   `poem-openapi`: OpenAPI (Swagger) for non-streaming HTTP APIs.
 *   **JavaScript:**
     *   `react-markdown`: For rendering chat responses.
+    *   `vitest`: Unit/component testing.
+    *   `playwright`: End-to-end testing.
 
 ## Safety & Sandbox
 1.  **Project Scope:** The application must strictly enforce that it does not read/write outside the `project_root` selected by the user.