Keyboard-accessible resize UI for media embeds — standalone buttons

This test verifies that media embeds can be resized without a pointing device using standalone toolbar buttons.

The editor uses MediaEmbedResize (full plugin including handles) with resizeMediaEmbed.toolbar configured to show individual buttons: resizeMediaEmbed:25, resizeMediaEmbed:50, resizeMediaEmbed:75, resizeMediaEmbed:original, and resizeMediaEmbed:custom.

Test plan

Preset resize (standalone buttons)

1. Click into the editor content to focus it.
2. Use Tab (or click) to select a media widget.
3. Use Tab to navigate to the media embed toolbar. Five resize buttons should be visible.
4. Press Space or Enter on one of the size buttons (e.g. 25%). Verify the media resizes.
5. The pressed button should appear toggled on (isOn: true). Other size buttons should be off.
6. Press Original — resize is removed, resizedWidth attribute disappears, no button is toggled.

Custom resize (balloon via standalone button)

1. Select a media widget using keyboard.
2. Navigate to the toolbar and press the Custom button.
3. Verify the custom resize balloon opens.
4. Type a valid number (e.g. 40) and press Enter. Verify the media resizes to 40% and the balloon closes.
5. Now none of the preset buttons should be toggled (because 40% doesn't match any preset).

Validation

1. Open the custom resize balloon via the Custom button.
2. Clear the input and press Enter. Verify error "The value must not be empty." appears.
3. Type abc and press Enter. Verify error "The value should be a plain number." appears.

Click outside

1. Open the custom resize balloon.
2. Click outside the balloon. Verify the balloon closes without changes.

Drag handles interop

1. Apply a preset size via a button.
2. Grab a drag handle and resize further.
3. Verify the drag starts from the correct current width.
4. After dragging, verify no preset button is toggled (the value no longer matches any preset).

Spotify embed

1. Select the Spotify widget (it has its own responsive layout and a minimum width).
2. Apply a preset size and a custom size. Verify the widget resizes without console errors and is not shrunk below its usable minimum width.
3. Press Original to reset.

Generic (non-previewable) media

1. Select the Facebook placeholder widget.
2. Press any preset size button. Verify the figure resizes without console errors.
3. Press Original to reset.