refactor: clean up migration code and improve widget display formatting

- Remove obsolete migrate_agent_runs_to_session_ids function from agents commands
- Add trailing empty line removal logic to ReadResultWidget for cleaner code display
- Improve code presentation consistency in UI components

src/components/ToolWidgets.tsx

@@ -474,6 +474,11 @@ export const ReadResultWidget: React.FC<{ content: string; filePath?: string }>
       }
     }
     
+    // Remove trailing empty lines
+    while (codeLines.length > 0 && codeLines[codeLines.length - 1] === '') {
+      codeLines.pop();
+    }
+    
     return {
       codeContent: codeLines.join('\n'),
       startLineNumber: minLineNumber === Infinity ? 1 : minLineNumber