Attachments subfolders?

[WanderingStar]

Is there an easy way to treat certain predictable subfolder paths as if links to them had {attach} prefixed?

For example, if I have an input hierarchy like:

content/posts/
└── 2025
    ├── 01
    │   ├── post1.md
    │   ├── post2.md
    │   └── attachments
    │       ├── img1.jpg
    │       ├── img2.jpg
    ├── 02
    │   ├── post3.md
    │   └── attachments
    │       ├── img3.jpg
    │       ├── img4.jpg

I'd like img1.jpg to end up in an attachments directory next to where post1.html is written. And img3.jpg to end up in an attachments directory next to where post3.html is written.

If the best answer is "add the {attach} prefix anytime a link starts with attachments", would a plugin be the best way to accomplish that? I don't want to add that prefix in the source documents because it will confuse my markdown editor.