Make area edges switchable in Debug UI

[leonardehrenfried]

Summary

@JohanEntur has requested that the very busy area edge view be made a bit more user friendly.

Therefore I moved the area edges to a different layer, styled them thinner and made it switchable.

It looks like this:

Screencast.From.2026-01-30.15-16-51.mp4

So for this reason

Unit tests

Expected style JSON updated.

Changelog

Skip.

Bumping the serialization version id

None.

[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 72.14%. Comparing base (5afceb5) to head (2362be4).
⚠️ Report is 1 commits behind head on dev-2.x.

Additional details and impacted files

@@            Coverage Diff             @@
##             dev-2.x    #7254   +/-   ##
==========================================
  Coverage      72.13%   72.14%           
- Complexity     21084    21090    +6     
==========================================
  Files           2297     2297           
  Lines          85233    85249   +16     
  Branches        8489     8489           
==========================================
+ Hits           61486    61504   +18     
- Misses         20767    20769    +2     
+ Partials        2980     2976    -4     

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