mbsync: Release ID [...] not found for album [...]

### Problem

Running this command:

```sh
$ beet mbsync
```

Led to this problem:

```
Release ID [...] not found for album [...] # (many instances of this)
```

The problem doesn't occur when reimporting the respective albums

### Setup

* OS: Fedora Linux 43 (Workstation Edition)
* Python version: 3.13.13
* beets version: 2.9.0 (and 2.8.0)
* Turning off plugins made problem go away (yes/no): no

My configuration (output of `beet config`) is:

```yaml
plugins:
- mbsync
- mbpseudox
- mbsync
```

Start by reproducing the issue with `beet mbsync` using the reported configuration, then compare its behavior with reimporting the affected albums. Trace the mbsync plugin's release lookup and determine why those release IDs are reported as missing; done means syncing completes without the repeated errors and matches reimport behavior.

Written by the indexing model from the issue text.