feat: Upgrade to Gradio 6.0.0.dev4 for improved MCP support

Updated from Gradio 5.49.1 to 6.0.0.dev4 (released 2 hours ago):
- requirements.txt: gradio[mcp]==6.0.0.dev4
- README.md: sdk_version: 6.0.0.dev4

Expected improvements:
- Fixed SSE transport ASGI errors on HuggingFace Spaces
- Better MCP streaming protocol handling
- Improved tool call reliability
- Enhanced stability for long-running operations

This should resolve the AssertionError in Starlette middleware
that was causing tool calls to fail intermittently.

README.md

@@ -4,7 +4,7 @@ emoji: 🤖
 colorFrom: blue
 colorTo: purple
 sdk: gradio
-sdk_version: 5.49.1
+sdk_version: 6.0.0.dev4
 app_port: 7860
 pinned: false
 license: agpl-3.0

requirements.txt

@@ -1,5 +1,5 @@
 # Core dependencies
-gradio[mcp]==5.49.1
+gradio[mcp]==6.0.0.dev4
 google-generativeai>=0.8.0
 datasets>=2.14.0
 pandas>=2.0.0