[Bug]: The Labeling pane says "Each class labels…" when only one class is visible #993

Before you start

• I searched the existing issues and did not find a duplicate.
• This is a bug report, not a usage question (questions belong in Discussions).

What happened?

In the Labeling pane's Content tab, the note under SQL Query, "Each class labels the features its own clause matches, so a feature can get a label from more than one.", shows whenever the layer has any class besides Default, even when that class is hidden. Then only one class labels the layer, so the note is about overlaps that cannot happen. The condition checks for extra classes (!labels.classes.is_empty() in crates/ui-egui/src/labelpane.rs), not for visible ones. CodeRabbit raised it on #967 after the push, and #967 had already been merged.

Steps to reproduce

1. Open the sample project, select Cities, and open the Labeling pane.
2. Tick "Label features in this layer".
3. Add a class with New, then untick Visible for it.
4. Choose Default again and look under SQL Query in the Content tab.

Expected behavior

The note shows only when more than one class is visible (Default included), as the classes the map draws: labels.in_order() filtered by visible.

How are you running RustGIS?

Desktop app (built from source)

Version

No response

Operating system, browser and graphics

macOS

Sample data

No response

Screenshots or logs

No response