refactor(agent): 将 tools 模块拆分为独立文件并优化导入路径

将 `tools.ts` 拆分为按功能划分的独立文件，并存放于 `tools/` 目录下，同时更新导入路径；优化 agent 系统提示语，移除冗余的「美图 Agent」前缀。

web/server/agent/tools/pipeline-status.ts

@@ -0,0 +1,22 @@
+import { execSync } from 'child_process';
+import { PIPELINE_SCRIPT, PROJECT_ROOT } from './shared';
+import type { ToolDefinition } from './types';
+
+export const pipelineStatus: ToolDefinition = {
+  name: 'pipeline_status',
+  description: '查看指定 manifest 的 pipeline 执行进度和各阶段状态',
+  input_schema: {
+    type: 'object',
+    properties: {
+      manifest: { type: 'string', description: 'manifest.json 的绝对路径' },
+    },
+    required: ['manifest'],
+  },
+  execute: async (params) => {
+    const { manifest } = params as { manifest: string };
+    const result = execSync(`node "${PIPELINE_SCRIPT}" status --manifest "${manifest}"`, {
+      cwd: PROJECT_ROOT, encoding: 'utf-8',
+    });
+    return result;
+  },
+};