fix: wait for auth session before connecting to realtime channel

On initial page load, the Supabase browser client's auth session may not
be ready yet (still loading from cookies). The Realtime channel subscription
silently fails without a valid access token. Now connect() awaits getSession()
first, which ensures the token is available and also refreshes expired tokens
on reconnect after inactivity.

Co-Authored-By: Claude Opus 4.5 <noreply@anthropic.com>

src/lib/collaboration/realtime.ts

@@ -77,6 +77,21 @@ export class RealtimeConnection {
     this.resetInactivityTimer()
     this.clearConnectionTimer()
 
+    // Ensure the Supabase client has a valid auth session before connecting.
+    // On initial page load, the session may still be loading from cookies.
+    try {
+      const { data: { session } } = await this.supabase.auth.getSession()
+      if (!session && !this.isDestroyed) {
+        // No session yet - wait briefly and retry
+        this.scheduleReconnect()
+        return
+      }
+    } catch {
+      // Session check failed - proceed anyway, channel will handle auth errors
+    }
+
+    if (this.isDestroyed || this.isPaused) return
+
     // Set a timeout: if we don't connect within CONNECTION_TIMEOUT_MS, retry
     this.connectionTimer = setTimeout(() => {
       if (this.isDestroyed || this.isPaused) return