fix: correct main entry path in rsbuild-plugin project.json

The main entry was pointing to the wrong path (packages/rsbuild-plugin/cli/src/index.ts)
when it should be packages/rsbuild-plugin/src/cli/index.ts. This was causing TypeScript
compilation errors during the build process.

🤖 Generated with [Claude Code](https://claude.ai/code)

Co-Authored-By: Claude <[email protected]>

Author: ScriptedAlchemy

packages/rsbuild-plugin/project.json

@@ -9,7 +9,7 @@
       "outputs": ["{options.outputPath}"],
       "options": {
         "outputPath": "packages/rsbuild-plugin/dist",
-        "main": "packages/rsbuild-plugin/cli/src/index.ts",
+        "main": "packages/rsbuild-plugin/src/cli/index.ts",
         "tsConfig": "packages/rsbuild-plugin/tsconfig.lib.json",
         "assets": [],
         "external": ["@module-federation/*"],