Merging: Limit to one network error alert

### Problem

On the merging page, a `window.alert()` message is displayed whenever the page fails to load the details of one of the works. Example:
`Network error; failed to load editions for /works/OL30200415W. Click OK to reload. `

Because network errors often result in multiple or all of the works failing to load, this can result in a high number of alerts being displayed, one after another. Only after I’ve dismissed all of the alerts does the page automatically reload.

### Reproducing the bug

_No response_

### Context

- Browser: Safari
- OS: iPadOS 18.1
- Logged in: Y
- Environment: prod

### Breakdown

#### Requirements Checklist
* [ ]

#### Related files

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#### Stakeholders

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#### Instructions for Contributors

- Please [run these commands](https://github.com/internetarchive/openlibrary/wiki/Git-Cheat-Sheet#working-on-your-branch) to ensure your repository is up to date **before** [creating a new branch](https://github.com/internetarchive/openlibrary/wiki/Git-Cheat-Sheet#making-changes-and-creating-a-pull-request) to work on this issue and **each time after** pushing code to Github, because the pre-commit bot may add commits to your PRs upstream.

Start by locating the merging page and the code that calls window.alert when edition details fail to load; no related files or tests are named in the issue. Reproduce the network-error case in the merging page and verify that the page presents only one alert before reloading.

Written by the indexing model from the issue text.