chore: update build config, linting, and add test infrastructure

Replace install -D with mkdir -p + install for macOS portability,
add vitest with jsdom and testing-library, configure eslint for
react-hooks v7 warnings, and add tokio test deps for Rust.

vitest.config.ts

@@ -0,0 +1,15 @@
+import { defineConfig } from "vitest/config";
+import path from "path";
+
+export default defineConfig({
+  test: {
+    globals: true,
+    environment: "jsdom",
+    setupFiles: ["./src/test/setup.ts"],
+  },
+  resolve: {
+    alias: {
+      "@": path.resolve(__dirname, "./src"),
+    },
+  },
+});