Inline edits to settings and book metadata silently don't stick in the v3 web UI

In the v3 beta web UI I edit a value inline, click the checkmark, and the change simply doesn't stick -- on the settings page with no visible error at all. On the book edit page I eventually caught a "failed to save changes" message, and editing metadata there doesn't write back to the file either.

Resolution: Two distinct failures look identical from the outside. The save can genuinely fail server-side: the book edit view does surface a "failed to save changes" error, so check there first, and turn on debug logging from the logs view in settings (it can be toggled live, but does not persist across restarts) to see the failing request. The more confusing case is focus-related -- clicking the save/checkmark button does not commit the field that still has focus, so an in-progress edit (removing a tag, for example) is dropped and only lands bundled with the next save. Workaround: click somewhere outside the field to blur it before saving, or press Ctrl+Enter, which commits reliably in every case. Both were v3 beta regressions in the web UI.