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.

eslint.config.js

@@ -6,7 +6,7 @@ import tseslint from 'typescript-eslint'
 import { defineConfig, globalIgnores } from 'eslint/config'
 
 export default defineConfig([
-  globalIgnores(['dist']),
+  globalIgnores(['dist', 'src-tauri']),
   {
     files: ['**/*.{ts,tsx}'],
     extends: [
@@ -19,5 +19,11 @@ export default defineConfig([
       ecmaVersion: 2020,
       globals: globals.browser,
     },
+    rules: {
+      // TODO: fix these incrementally — pre-existing violations from react-hooks v7 upgrade
+      'react-hooks/set-state-in-effect': 'warn',
+      'react-hooks/refs': 'warn',
+      'react-refresh/only-export-components': ['warn', { allowConstantExport: true }],
+    },
   },
 ])