documentation: (Toy) use generic parser in Toy

[superlopuh]

Exercises the genericness of proposed generic parser infrastructure.

Note stacked PR.

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[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 90.40%. Comparing base (8459f95) to head (a6f8b14).
Report is 3 commits behind head on main.

Additional details and impacted files

@@           Coverage Diff           @@
##             main    #3596   +/-   ##
=======================================
  Coverage   90.40%   90.40%           
=======================================
  Files         470      471    +1     
  Lines       59127    59112   -15     
  Branches     5610     5607    -3     
=======================================
- Hits        53452    53442   -10     
+ Misses       4232     4230    -2     
+ Partials     1443     1440    -3     

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[math-fehr]

I see number of lines going down, I'm happy