Use correct submission method for fasttrack inlines

[jacbn]

Inline questions should be submitted via submitInlineRegion; FastTrack questions were using a different submit button that did not have the onClick override that used to be in place for inline regions on the main button. This PR refactors the flow a little so all question attempts pass through the same onSubmit handler, ensuring both regular and FT inline questions submit using the same logic.

[codecov]

Codecov Report

❌ Patch coverage is 0% with 5 lines in your changes missing coverage. Please review.
✅ Project coverage is 43.53%. Comparing base (db64a99) to head (5ef0de6).

Files with missing lines	Patch %	Lines
src/app/components/content/IsaacQuestion.tsx	0.00%	5 Missing ⚠️

Additional details and impacted files

@@           Coverage Diff           @@
##             main    #2359   +/-   ##
=======================================
  Coverage   43.53%   43.53%           
=======================================
  Files         601      601           
  Lines       25887    25887           
  Branches     8622     8600   -22     
=======================================
  Hits        11269    11269           
  Misses      14561    14561           
  Partials       57       57           

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[barna-isaac]

Looks good! Also changes the focused element after submission for an inline question that's not fast-track, but I don't see that being a bad change (pressing Tab after submit previously landed on the flag, it now lands on the feedback navigation).