fix: Resolve TypeScript error with atp_cid used before assignment

- Added rootPost variable to store first post's URI and CID
- Fixed thread reply references to use rootPost instead of atp_cid before it's assigned
- Resolves production build TypeScript error

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

Co-Authored-By: Claude <noreply@anthropic.com>

app/api/nodes/route.ts

@@ -133,6 +133,7 @@ export async function POST(request: NextRequest) {
 
     // Create the thread posts
     let previousPost: { uri: string; cid: string } | null = null;
+    let rootPost: { uri: string; cid: string } | null = null;
     const threadUris: string[] = [];
 
     for (let i = 0; i < chunks.length; i++) {
@@ -169,12 +170,10 @@ export async function POST(request: NextRequest) {
         tags: ['ponderants-node'],
       };
 
-      // If not first post, add reply reference
-      if (previousPost && threadUris.length > 0) {
-        // Get the first post (root) CID from the stored thread data
-        const rootCid = atp_cid; // First post's CID
+      // If not first post, add reply reference to create a thread
+      if (previousPost && rootPost) {
         postRecord.reply = {
-          root: { uri: threadUris[0], cid: rootCid },
+          root: { uri: rootPost.uri, cid: rootPost.cid },
           parent: { uri: previousPost.uri, cid: previousPost.cid },
         };
       }
@@ -189,8 +188,9 @@ export async function POST(request: NextRequest) {
       threadUris.push(response.data.uri);
       previousPost = { uri: response.data.uri, cid: response.data.cid };
 
-      // Store the first post's URI as the main atp_uri
+      // Store the first post's URI and CID as both the root and the main atp_uri
       if (isFirstPost) {
+        rootPost = { uri: response.data.uri, cid: response.data.cid };
         atp_uri = response.data.uri;
         atp_cid = response.data.cid;
       }