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/generate-images.ts

@@ -0,0 +1,46 @@
+import { execSync } from 'child_process';
+import { runInit, loadJSON, PIPELINE_SCRIPT, PROJECT_ROOT } from './shared';
+import type { ToolDefinition } from './types';
+
+export const generateImages: ToolDefinition = {
+  name: 'generate_images',
+  description: '文生图：根据文本提示词生成图片。内部创建临时 manifest 并调用 pipeline images 阶段，支持批量生成。生成结果写入 output 目录，返回图片文件路径列表。',
+  input_schema: {
+    type: 'object',
+    properties: {
+      accountId: { type: 'string', description: '账号ID，用于继承模型、参考图等配置' },
+      prompt: { type: 'string', description: '图片提示词（imagePrompt），描述要生成的图片内容' },
+      count: { type: 'number', description: '生成图片数量，默认 1' },
+      imageModel: { type: 'string', description: '生图模型（可选，默认继承账号配置）: gemini, mj, gpt-image, kling' },
+    },
+    required: ['accountId', 'prompt'],
+  },
+  execute: async (params) => {
+    const { accountId, prompt, count, imageModel } = params as Record<string, unknown>;
+    const num = Math.max(1, Number(count) || 1);
+    const items = Array.from({ length: num }, (_, i) => ({
+      id: i + 1,
+      shotDesc: prompt as string,
+      script: '',
+      imagePrompt: prompt as string,
+      keyword: 'generated',
+    }));
+    const manifestPath = runInit({
+      account: accountId as string,
+      mode: 'single',
+      items,
+      imageModel: imageModel as string | undefined,
+    });
+    execSync(`node "${PIPELINE_SCRIPT}" run --manifest "${manifestPath}" --phase images`, {
+      cwd: PROJECT_ROOT, encoding: 'utf-8',
+    });
+    const manifest = loadJSON(manifestPath) as { items?: Array<{ id: number; file?: string; candidates?: string[]; status?: string }> };
+    const results = (manifest.items || []).map((item) => ({
+      id: item.id,
+      file: item.file || null,
+      candidates: item.candidates || [],
+      status: item.status,
+    }));
+    return JSON.stringify({ manifestPath, images: results }, null, 2);
+  },
+};