Currently, using `snapm snapset rename` on a bootable snapshot set leaves the original boot entries behind:

<img width="720" height="400" alt="Image" src="https://github.com/user-attachments/assets/4092642b-b464-46d4-aa64-7c64743a7488" />

(snapset `before-ugprade` was renamed to `before-upgrade`, deleted, and re-created).

This is fixable via `sed`:

```bash
$ sed i 's/OLD_NAME/NEW_NAME/g' /boot/loader/entries/$MACHINE_ID$BOOT_ID-$VERSION.conf
```

A subsequent `boom list` will detect the incorrect `$BOOT_ID` and re-write the entry, but this is a kinda kludgy workaround.

A rename should delete and re-create the boot and revert entries if present.