后端：附件读取/下载端点 + 删除端点 + addAttachments 落库去重 (tsk_tttdU3VLCy50)

- store.addAttachments：按 path 去重（later-wins），消除重传产生的悬空元数据
- store.removeAttachment：按磁盘文件名（basename(path)）移除元数据，返回 removed
- GET /api/tasks/:id/attachments/:name：inline 预览，?download=1 触发下载（RFC5987 文件名）
- DELETE /api/tasks/:id/attachments/:name：先删元数据再尽力删磁盘文件
- 只服务元数据登记过的附件 + resolve/startsWith 前缀校验，杜绝目录穿越
- 新增 test/attachments.test.ts（去重/读取/下载/删除/穿越/丢失/端到端上传去重）

Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>

src/api/server.ts

@@ -12,10 +12,10 @@ import { acceptAndMerge } from '../executor/exec-merge.js';
 import { createWorktree, git } from '../executor/worktree.js';
 import { resolveLogo, LOGO_MIME } from './logo.js';
 import { readTranscript, TranscriptError } from '../executor/transcript.js';
-import { createReadStream, createWriteStream, mkdirSync, readFileSync, statSync } from 'node:fs';
+import { createReadStream, createWriteStream, mkdirSync, readFileSync, rmSync, statSync } from 'node:fs';
 import { transcriptDir } from '../executor/cc.js';
 import { homedir } from 'node:os';
-import { join, basename } from 'node:path';
+import { join, basename, resolve, sep } from 'node:path';
 import { pipeline } from 'node:stream/promises';
 import multipart from '@fastify/multipart';
 import { createUsageFetcher, type UsageInfo } from '../daemon/usage.js';
@@ -356,6 +356,48 @@ export function buildServer(opts: ApiOptions): FastifyInstance {
     return { attachments: store.addAttachments(id, saved) };
   });
 
+  // 附件读取/预览/下载：默认 inline（图片可 <img> 预览）；?download=1 触发下载。
+  // 标识符为磁盘文件名 :name（= basename(att.path)），只服务元数据里登记过的附件。
+  app.get('/api/tasks/:id/attachments/:name', (req, reply) => {
+    const { id, name } = req.params as { id: string; name: string };
+    const task = store.getTask(id);
+    if (!task) return reply.code(404).send({ error: `任务不存在: ${id}` });
+    const att = (task.attachments ?? []).find((a) => basename(a.path) === name);
+    if (!att) return reply.code(404).send({ error: `附件不存在: ${name}` });
+
+    const abs = resolve(join(dataDir(), att.path));
+    // 纵深防御：解析后必须仍在该任务 attachments 目录内
+    const baseDir = resolve(join(dataDir(), 'tasks', id, 'attachments'));
+    if (abs !== baseDir && !abs.startsWith(baseDir + sep))
+      return reply.code(400).send({ error: '附件路径越界' });
+    let st;
+    try { st = statSync(abs); } catch { return reply.code(404).send({ error: '附件文件已丢失' }); }
+
+    const dl = (req.query as { download?: string }).download;
+    const fallbackName = att.name || name;
+    reply
+      .header('cache-control', 'private, max-age=300')
+      .header('content-length', String(st.size))
+      .header('content-disposition',
+        `${dl ? 'attachment' : 'inline'}; filename*=UTF-8''${encodeURIComponent(fallbackName)}`)
+      .type(att.type || 'application/octet-stream');
+    return reply.send(createReadStream(abs));
+  });
+
+  // 删除单个附件：先删元数据（拿到 removed），再尽力删磁盘文件
+  app.delete('/api/tasks/:id/attachments/:name', (req, reply) => {
+    const { id, name } = req.params as { id: string; name: string };
+    if (!store.getTask(id)) return reply.code(404).send({ error: `任务不存在: ${id}` });
+    const { attachments, removed } = store.removeAttachment(id, name);
+    if (!removed) return reply.code(404).send({ error: `附件不存在: ${name}` });
+    const abs = resolve(join(dataDir(), removed.path));
+    const baseDir = resolve(join(dataDir(), 'tasks', id, 'attachments'));
+    if (abs === baseDir || abs.startsWith(baseDir + sep)) {
+      try { rmSync(abs, { force: true }); } catch { /* 磁盘文件已不在，忽略 */ }
+    }
+    return { attachments };
+  });
+
   // 人工接管：准备（或复用）任务 worktree，返回用户在自己终端起交互式 claude 的命令。
   // 适用卡住/需人工的任务——人接手手动改。不在 daemon 内起交互会话（无 TTY）。
   app.post('/api/tasks/:id/takeover', async (req, reply) => {