feat(cli): enforce flags validation

[wellwelwel]

Closes #647.

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To enable this feature, use the --enforce or -x flags.

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• The choice for enforce instead of strict (my preference) is to avoid ambiguity with the strict assertion method.
• Although it's interesting to display warnings for user mistakes by default, at the moment I have no intention to show warnings due to flags unknown to Poku (perhaps in the next major version).

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Important

This option is dynamic (not limited to a single effect) and is intended to ensure that the execution is valid and secure before continuing with the tests.

[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 98.73%. Comparing base (203fb45) to head (3a4d764).
Report is 3 commits behind head on main.

Additional details and impacted files

@@            Coverage Diff             @@
##             main     #699      +/-   ##
==========================================
+ Coverage   98.58%   98.73%   +0.15%     
==========================================
  Files          36       36              
  Lines        1902     1902              
  Branches        9       11       +2     
==========================================
+ Hits         1875     1878       +3     
+ Misses         18       16       -2     
+ Partials        9        8       -1     

Flag	Coverage Δ
linux	98.52% <ø> (?)
osx	98.58% <ø> (ø)
windows	98.52% <ø> (?)

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