Fix lerna config and exclude test files from build

- Remove deprecated useWorkspaces option from lerna.json (lerna v8+)
- Exclude test files from TypeScript compilation in tsconfig.json
- Update .npmignore to exclude test directory and vitest config from npm package

This fixes the CI build pipeline error and ensures test files are not
included in the compiled output or published package.

Author: claude

lerna.json

@@ -1,6 +1,5 @@
 {
   "$schema": "node_modules/lerna/schemas/lerna-schema.json",
   "useNx": true,
-  "useWorkspaces": true,
   "version": "0.0.0"
 }

packages/react-snowfall/.npmignore

@@ -3,7 +3,10 @@ node_modules
 assets
 demo
 src/__mocks__
+src/test
+src/**/*.test.ts
 src/**/*.test.tsx
+vitest.config.ts
 .babelrc
 .eslintrc.js
 .prettierrc.js

packages/react-snowfall/tsconfig.json

@@ -13,4 +13,5 @@
     "sourceMap": true,
   },
   "include": ["src"],
+  "exclude": ["src/test", "**/*.test.ts", "**/*.test.tsx"]
 }