Post button disabled after streaming ends

the post button in the composer is disabled after the streaming ends. There's a bug there.

I've created PR #125 to fix the bug. Here's a summary of the changes:

##Problem

The post button in the composer was disabled after an LLM streaming response ended. This happened because hasStreamingComment was computed server-side during page render (by checking postComments.some(c => c.streamStatus === "streaming")) and passed as a prop. When the streaming finished on the client side, this value never updated since it was a static server-side value.

##Solution

I introduced a shared React context (StreamingStateContext) that:

1. streaming-state-context.tsx - New file that creates a context to track which comments are currently streaming. It provides:

   • hasStreamingComment - boolean indicating if any comment is streaming
   • setCommentStreaming(commentId, isStreaming) - function to update streaming state

2. streaming-content.tsx - Updated StreamingCommentProvider to sync its local isStreaming state to the shared context using a useEffect hook. When streaming ends (status changes from "streaming" to "ready"), the context is updated.

3. post-composer.tsx - Changed to use useHasStreamingComment() hook instead of receiving hasStreamingComment as a prop

4. page.tsx - Wrapped the content with StreamingStateProvider initialized with the server-side streaming comment IDs

This ensures the post button reactively enables when the streaming actually completes on the client side.