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/shared.ts

@@ -0,0 +1,46 @@
+import path from 'path';
+import fs from 'fs';
+import { fileURLToPath } from 'url';
+import os from 'os';
+import { execSync } from 'child_process';
+
+const __filename = fileURLToPath(import.meta.url);
+const __dirname = path.dirname(__filename);
+
+export const PROJECT_ROOT = path.resolve(__dirname, '..', '..', '..', '..');
+export const PIPELINE_SCRIPT = path.join(PROJECT_ROOT, '.claude', 'skills', 'video-from-script', 'scripts', 'pipeline.js');
+export const ACCOUNTS_DIR = path.join(PROJECT_ROOT, 'accounts');
+export const OUTPUT_DIR = path.join(PROJECT_ROOT, 'output');
+
+export function loadJSON(filePath: string): unknown {
+  return JSON.parse(fs.readFileSync(filePath, 'utf-8'));
+}
+
+export function runInit(params: {
+  account: string;
+  mode: string;
+  items: unknown[];
+  imageModel?: string;
+  videoModel?: string;
+  format?: string;
+}): string {
+  const tmpFile = path.join(os.tmpdir(), `pipeline-items-${Date.now()}.json`);
+  fs.writeFileSync(tmpFile, JSON.stringify(params.items), 'utf-8');
+  try {
+    const args = [
+      `"${PIPELINE_SCRIPT}"`, 'init',
+      `--account "${params.account}"`,
+      `--mode ${params.mode}`,
+      `--items-file "${tmpFile}"`,
+      params.imageModel ? `--image-model ${params.imageModel}` : '',
+      params.videoModel ? `--video-model ${params.videoModel}` : '',
+      params.format ? `--format ${params.format}` : '',
+    ].filter(Boolean).join(' ');
+    const output = execSync(`node ${args}`, { cwd: PROJECT_ROOT, encoding: 'utf-8' });
+    const match = output.match(/Manifest 已创建: (.+)/);
+    if (!match) throw new Error(`Failed to parse manifest path from init output: ${output}`);
+    return match[1].trim();
+  } finally {
+    try { fs.unlinkSync(tmpFile); } catch { /* ignore */ }
+  }
+}