feat(uploads): prompt uploads take documents

The Attach button, the Compose and paste-dialog pickers, terminal drop and the
clipboard now take documents beside images and videos: the office formats
pdf/docx/pptx/xlsx/zip and the text family txt/md/csv/tsv/json/log/yaml/yml/xml.

A document is admitted by its name's extension (the MIME a phone attaches to a
.md is anyone's guess), buffered under the same 50MB image cap, and judged on
its bytes by the same fail-closed sniffer: a magic-number signature for the
binary formats, UTF-8 with no NUL byte for text. It is saved under a sanitized
stem of its name, so Q3 report.pdf is findable as paste-<ts>-<hex>-Q3-report.pdf.

sh/py/js/html are refused by name with a clear 400. That is a scope choice, not
a security property: file-raw already serves non-media text inert, so this keeps
the server from storing what it would serve or an agent could run, and html and
svg are the ones deliberately kept out. One client classifier (_promptAttachKind)
now returns image, video or document, and the server's dispatch mirrors it: an
image MIME wins whatever the name says, a document extension takes the document
branch, and a foreign extension with no image MIME is refused only after the
image sniff fails, so nothing the image path accepted by its bytes is lost.

README.zh-CN.md

@@ -276,7 +276,7 @@ codeman service install           # systemd/launchd 服务：重启后自动回
 ### 4. 与智能体对话
 
 - **直接在终端输入提示** —— 即使跨越重连，输入也是精确一次送达（连接中断绝不会丢失或重复发送提示）。
-- **粘贴、拖放或附加图片和视频**，直接进入会话。它们保存在工作区里一个隐藏的 `.codeman-uploads/` 文件夹中（它在 git 里会忽略自己，7 天后被清理），文件路径会落在你的提示里，但不会自动发送。
+- **粘贴、拖放或附加图片、视频和文档**（PDF、Office 文件、zip 和纯文本），直接进入会话。它们保存在工作区里一个隐藏的 `.codeman-uploads/` 文件夹中（它在 git 里会忽略自己，7 天后被清理），文件路径会落在你的提示里，但不会自动发送。
 - **语音输入** —— `Ctrl+Shift+V`（Deepgram Nova-3，或者直接用这台机器的 Claude Code 登录、不需要任何 API key；自动静音停止）。
 - **附件** —— 注册外部文件/文档，并内联预览 Office/PDF；智能体打印出的任何文件路径都可以点击，终端里和对话视图里都行，包括 `~/` 路径、相对路径和被折成多行的路径。`.html` 报告会以真实网页打开，Markdown 会渲染后打开，文件夹则以其文件的网格打开。
 - **需要你的时候** —— 标签会变黄（等待输入）或变红（有个问题挡住了它）。**审批收件箱（Approvals Inbox）**（可选启用）把所有会话里等着你的提示排成一个队列，可以从页头的铃铛或手机首页直接作答；🧠 **Read My Mind**（可选启用）会根据这个 case 的目标和最近的工作替你起草下一条提示。