[Screen Reader][Firefox] Narrator focus outline does not fully cover block items and End block group

[Nina-1210]

Describe the bug
When using Windows 11 Narrator in Firefox, the screen reader focus (blue outline) does not fully cover the focused block item in the toolbox or the End block group in the workspace during keyboard navigation.

Steps to reproduce the behavior:

1. Enable Windows 11 Narrator.
2. Navigate to Microsoft MakeCode for micro:bit.
3. Open any existing Blocks project.
4. Press Ctrl + B to open the global area menu.
5. Press 3 to move focus to the toolbox.
6. Press Caps Lock + Space to turn off scan mode.
7. Use Arrow keys (Right/Down) to navigate block items (e.g., Basic category).
8. Observe the Narrator focus outline.
9. Use Tab / Down Arrow to navigate to the End block group in the workspace.
10. Observe the Narrator focus outline.

Actual behavior
The Narrator focus outline does not fully cover the focused block item or End block group in Firefox.

Expected behavior
The Narrator focus outline should fully cover the focused element (block item and End block group), consistent with behavior in other browsers.

Screen Recording
https://github.com/user-attachments/assets/1303b7d0-33ba-4d24-bd07-8221a0f196b2

Additional context
1.OS: Windows 11 25H2
2.Browser: Firefox
3.makecode.microbit.org version: 8.1.25
4.Microsoft MakeCode version: 12.3.20

[abchatra]

@microbit-matt-hillsdon @microbit-robert ?

[microbit-robert]

@abchatra Related to #6951

A fix has been merged into Blockly so should be included in the next release.

[microbit-robert]

This is a problem in Firefox for both Windows Narrator and VoiceOver and could well be a Firefox bug. I suspect it's due to the transforms on SVG elements. I will investigate a bit more but I don't think we'll address this for the release. The impact is going to be for users with low vision where the screen reader cursor tracking might be useful, in which case we should suggest an alternative browser for now.

Update: Two things cause this. Translate and scale which are applied on the flyout SVG and the flyout listbox element, respectively. Translate can be fixed by using top / left etc instead, scale cannot. Again, this looks like a Firefox bug.