fix: ChatBubble crash and DeepSeek API compatibility

- Fix ChatBubble to handle non-string content with String() wrapper
- Fix API route to use generateText for non-streaming requests
- Add @ai-sdk/openai-compatible for non-OpenAI providers (DeepSeek, etc.)
- Use Chat Completions API instead of Responses API for compatible providers
- Update ChatBubble tests and fix component exports to kebab-case
- Remove stale PascalCase ChatBubble.tsx file

package.json

@@ -12,6 +12,7 @@
   },
   "dependencies": {
     "@ai-sdk/openai": "^3.0.14",
+    "@ai-sdk/openai-compatible": "^2.0.18",
     "@radix-ui/react-alert-dialog": "^1.1.15",
     "@radix-ui/react-dialog": "^1.1.15",
     "@radix-ui/react-label": "^2.1.8",