fix(chat-ui): add CSS export to package.json and fix import path

The @import in main.css failed because ./src/chat-ui.css wasn't
in the exports field. Add explicit export and use correct path.

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

apps/main/src/main.css

@@ -1,6 +1,6 @@
 @import "tailwindcss";
 @import "tw-animate-css";
-@import "@xtablo/chat-ui/src/chat-ui.css";
+@import "@xtablo/chat-ui/chat-ui.css";
 
 @source "../../../packages/chat-ui/src/**/*.{ts,tsx}";
 

packages/chat-ui/package.json

@@ -5,6 +5,7 @@
   "type": "module",
   "exports": {
     ".": "./src/index.ts",
+    "./chat-ui.css": "./src/chat-ui.css",
     "./components/*": "./src/components/*.tsx",
     "./hooks": "./src/hooks.ts",
     "./security": "./src/security.ts",