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/tsconfig.app.json

@@ -4,7 +4,7 @@
     "target": "es2023",
     "lib": ["ES2023", "DOM", "DOM.Iterable"],
     "module": "esnext",
-    "types": ["vite/client"],
+    "types": ["vite/client", "vitest/globals", "@testing-library/jest-dom"],
     "skipLibCheck": true,
 
     /* Bundler mode */