test(coverage): bootstrap vitest unit infra and add tests at 90%+ per file (#1245) (#1269)

* test(coverage): bootstrap vitest unit infra and add tests at 90%+ per file (#1245)

Establishes the unit-test runtime AGENTS.md mandates: a vitest "unit"
project alongside the existing storybook project, RTL + jest-dom +
happy-dom, a Mantine-aware render helper, and a 90%-line per-file
coverage gate enforced by CI. Adds 66 test files covering all 62
components under elements/groups/screens/views, plus core/mcp and
clients/web/src/utils. Total: 577 tests, 98.7% line coverage globally.

Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>

* test(coverage): address PR #1269 review feedback

- AGENTS.md: correct coverage gate description (lines ≥ 90, statements ≥ 85,
  functions ≥ 80, branches ≥ 50) with rationale for the relaxed branch
  threshold
- InspectorView.test.tsx: document what the Math.random() mock values
  (0.1 / 0.99) control vs. STUB_SUCCESS_RATE in InspectorView.tsx
- vite.config.ts / tsconfig.test.json: drop unused `globals: true` and the
  `vitest/globals` type now that every test file imports describe/it/expect/vi
  explicitly; manual `afterEach(cleanup)` in setup.ts remains required because
  testing-library auto-cleanup relies on globalThis.afterEach

Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>

---------

Co-authored-by: Claude Opus 4.7 (1M context) <noreply@anthropic.com>

clients/web/package.json

@@ -9,10 +9,14 @@
     "lint": "eslint .",
     "format": "prettier --write src",
     "format:check": "prettier --check src",
-    "validate": "npm run format:check && npm run lint && npm run build",
+    "validate": "npm run format:check && npm run lint && npm run build && npm run test:coverage",
     "preview": "vite preview",
     "storybook": "storybook dev -p 6006",
-    "build-storybook": "storybook build"
+    "build-storybook": "storybook build",
+    "test": "vitest run --project=unit",
+    "test:watch": "vitest --project=unit",
+    "test:coverage": "vitest run --project=unit --coverage",
+    "test:storybook": "vitest run --project=storybook"
   },
   "dependencies": {
     "@emotion/react": "^11.14.0",
@@ -35,12 +39,16 @@
     "@storybook/addon-onboarding": "^10.2.19",
     "@storybook/addon-vitest": "^10.2.19",
     "@storybook/react-vite": "^10.2.19",
+    "@testing-library/jest-dom": "^6.9.1",
+    "@testing-library/react": "^16.3.2",
+    "@testing-library/user-event": "^14.6.1",
     "@types/node": "^24.12.0",
     "@types/react": "^19.2.14",
     "@types/react-dom": "^19.2.3",
     "@vitejs/plugin-react": "^6.0.0",
     "@vitest/browser-playwright": "^4.1.0",
     "@vitest/coverage-v8": "^4.1.0",
+    "happy-dom": "^20.9.0",
     "eslint": "^9.39.4",
     "eslint-plugin-react-hooks": "^7.0.1",
     "eslint-plugin-react-refresh": "^0.5.2",