sync virtual file without opening

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## Feature request

**Which Nextcloud Version are you currently using:** 29.0.7

**Describe the solution you'd like**

The ability to initiate sync of file but without opening it.

The current mechanism relies on using `xdg-open` (or `mimeopen`) for opening a file: the `.nextcloud` file extension (on linux) chains through several mime-related files, eventually resolving to using `/usr/bin/nextcloud` on the file. Its behavior is to sync it to the local directory and then open the file. (If you're curious to which files, read https://github.com/nextcloud/desktop/issues/3668#issuecomment-2377036151.)

However, in my use-case I need to open it within the VM, which is certainly not something nextcloud should try to implement. Currently I have to open it in linux, which opens in what linux thinks is the appropriate app (it's insufficient but doesn't crash). I then close the app, then open the file from within the windows-guest VM (with a shared-folder to get to the real file).

A clear and concise description of what you want to happen.

**Describe alternatives you've considered**

- `nextcloudcmd` only syncs whole directories, it does not support individual files; even if it did, I'm not certain that it signals that the file is the realization of a virtual file, and therefore not a change. I would not want this to cause an unnecessary false-signal that the newly downloaded is "new" and needs to be uploaded.
- anything using `webdav` falls prey to the same false-signal that the downloaded file is "new" or "changed", which would overwrite the file on the server; at best this is inefficient.
- I have tried to hack a script that "opens" it (using the default `xdg-open`/`mimeopen` mechanism) and immediately close the mime-defined application, but this is just a hack and often doesn't catch it quite in time.

**Additional context**

- It is not unheard of that opening the file imposes some change on its contents, either by accident (such as imperfect MS-Office emulation in LibreOffice/OpenOffice, bug reports almost certainly) or by design (I have no example at this time). In this case, syncing the file is the only thing desired, anything more is irreversible.
- My use-case to open it within a VM is just mine, I think the request is still relevant. For instance, if I'm syncing to the local drive and will then take it to another machine (on which I'm not running a nextcloud desktop client), it might be that the file _cannot_ be run on the local system due to any number of reasons (such as the required software not installed alongside the desktop client).