test(web): scaffold vitest + RTL with Orchestrator seed suite (DEBT-043)

Wire vitest 4 + jsdom + @testing-library/{react,jest-dom,user-event}
+ @vitest/coverage-v8 through vite.config.ts (defineConfig from
vitest/config). src/test/setup.ts registers jest-dom matchers and
RTL cleanup. tsconfig.app.json picks up vitest/globals types.

Seed suite Orchestrator.test.tsx covers the three regressions
called out in DEBT-043: empty-state render, kind-filter toggling
triggers a scoped refetch, mocked stream callback prepends a row.

decnet_web/package.json

@@ -7,7 +7,10 @@
     "dev": "vite",
     "build": "tsc -b && vite build",
     "lint": "eslint .",
-    "preview": "vite preview"
+    "preview": "vite preview",
+    "test": "vitest",
+    "test:run": "vitest run",
+    "coverage": "vitest run --coverage"
   },
   "dependencies": {
     "asciinema-player": "^3.8.0",
@@ -20,16 +23,22 @@
   },
   "devDependencies": {
     "@eslint/js": "^9.39.4",
+    "@testing-library/jest-dom": "^6.9.1",
+    "@testing-library/react": "^16.3.2",
+    "@testing-library/user-event": "^14.6.1",
     "@types/node": "^24.12.2",
     "@types/react": "^19.2.14",
     "@types/react-dom": "^19.2.3",
     "@vitejs/plugin-react": "^6.0.1",
+    "@vitest/coverage-v8": "^4.1.5",
     "eslint": "^9.39.4",
     "eslint-plugin-react-hooks": "^7.0.1",
     "eslint-plugin-react-refresh": "^0.5.2",
     "globals": "^17.4.0",
+    "jsdom": "^29.1.1",
     "typescript": "~6.0.2",
     "typescript-eslint": "^8.58.0",
-    "vite": "^8.0.4"
+    "vite": "^8.0.4",
+    "vitest": "^4.1.5"
   }
 }