refactor(core): rename TaskTool to AgentTool

Rename the Task tool to Agent tool for clearer semantics and better
alignment with industry terminology. This change includes:

- Rename TaskTool -> AgentTool, TaskParams -> AgentParams
- Rename TaskResultDisplay -> AgentResultDisplay
- Add 'Explore' built-in agent for read-only codebase exploration
- Add backward compatibility mappings for legacy tool names
- Improve Agent tool description with clearer usage guidelines
- Add case-insensitive agent name matching
- Fallback to built-in agents when subagent loading fails

Co-authored-by: Qwen-Coder <qwen-coder@alibabacloud.com>

packages/cli/src/ui/utils/resumeHistoryUtils.ts

@@ -100,6 +100,10 @@ function formatToolDescription(
     const invocation = tool.build(args);
     return invocation.getDescription();
   } catch {
+    // Fallback: use the description arg directly if available
+    if (typeof args['description'] === 'string') {
+      return args['description'];
+    }
     return '';
   }
 }