[Feature]: web read / weixin download 执行后明确显示文件保存路径，并完善 skill 文档说明

[uxfion]

Feature Description

opencli web read 和 opencli weixin download 执行成功后，仅在终端打印元数据摘要，没有任何关于文件保存位置的提示：

- title: <page title>
  author: '-'
  status: success
  size: 12.4 KB

希望在输出中明确显示内容保存到了哪个本地路径，并在 skill 文档中补充说明。

Use Case

As an AI agent user, I want to know where the saved file is after running opencli web read, so that I can immediately read the local file instead of mistakenly assuming the command failed to retrieve content.

当前 agent 默认假设命令输出走 stdout，看到终端没有实质内容时，会误判为抓取失败，进而反复重试或放弃，而实际上文件已经保存到了本地。如果输出中包含保存路径，agent 可以直接读取本地文件，避免不必要的重试。

Proposed Solution

1. 在终端输出中补充保存路径

在命令成功后的元数据摘要中新增 saved 字段：

- title: <page title>
  status: success
  size: 12.4 KB
  saved: ./web-articles/<title>/<title>.md

2. 完善 skill 文档说明

在 SKILL.md 的 adapter 表格中补充说明：

# Before
| **web**    | 🌐 | `read` — any URL to Markdown              |
| **weixin** | 🌐 | `download` — 公众号 article to Markdown   |

# After
| **web**    | 🌐 | `read` — any URL to Markdown ⚠️ 内容保存到本地文件，非 stdout |
| **weixin** | 🌐 | `download` — 公众号 article to Markdown ⚠️ 内容保存到本地文件，非 stdout |

在 commands.md 的示例注释中补充说明：

# Before
opencli web read --url "https://..."
opencli weixin download --url "https://mp.weixin.qq.com/s/xxx"

# After
opencli web read --url "https://..."      # 保存到 ./web-articles/，非 stdout
opencli weixin download --url "https://mp.weixin.qq.com/s/xxx"  # 保存到 ./web-articles/，非 stdout

Alternatives Considered

将内容改为直接输出到 stdout：对脚本管道友好，但大文章会导致终端输出过多，不适合交互场景。所以在stdout中提到保存路径是最好的解决办法。

[Astro-Han]

This request makes sense.

I checked the current implementation. opencli web read and opencli weixin download already write content to local files, and both commands already support an --output directory. But the returned result only shows summary fields like title, author, publish_time, status, and size. It does not show the saved file path.

So the confusion here is real. If an agent expects content on stdout, the current output can look like a failed fetch even when the file was written successfully.

A direct fix would be to add a saved or file field to the result, then update the docs to say clearly that these commands save to local files by default instead of printing the full content to stdout.

[Benjamin-eecs]

Opened a fix in #1042.

Added a saved field to ArticleDownloadResult that returns the local file path on success (or - on failure). Also updated columns for both web/read and weixin/download, and updated SKILL.md and commands.md to clarify that content is saved to local files.

@Astro-Han @jackwener would appreciate a review if you have time.