fix(backlog-plan): extract result text from Cursor provider

- Add handler for type=result messages in stream processing
- Cursor provider sends final accumulated text in msg.result
- Backlog plan was only handling assistant messages
- Now matches pattern used by github validation and suggestions
- Fixes "cursor cli parsing failed" error

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

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

apps/server/src/routes/backlog-plan/generate-plan.ts

@@ -146,6 +146,11 @@ export async function generateBacklogPlan(
             }
           }
         }
+      } else if (msg.type === 'result' && msg.subtype === 'success' && msg.result) {
+        // Use result if it's a final accumulated message (from Cursor provider)
+        if (msg.result.length > responseText.length) {
+          responseText = msg.result;
+        }
       }
     }