fix: allow the screen to be filled exactly and fix off by one errors

[tertsdiepraam]

A fix for eza-community/eza#799 and another case I found along the way.

This change does not seem to break anything in uutils.

[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Comparison is base (15fc61c) 47.87% compared to head (1522e5f) 53.46%.
Report is 3 commits behind head on main.

Additional details and impacted files

@@            Coverage Diff             @@
##             main      #34      +/-   ##
==========================================
+ Coverage   47.87%   53.46%   +5.59%     
==========================================
  Files           4        4              
  Lines         470      490      +20     
  Branches       79       80       +1     
==========================================
+ Hits          225      262      +37     
- Misses        208      209       +1     
+ Partials       37       19      -18     

Flag	Coverage Δ
macos_latest	53.26% <95.83%> (+6.45%)	⬆️
ubuntu_latest	48.57% <91.66%> (+1.76%)	⬆️
windows_latest	1.63% <0.00%> (-0.07%)	⬇️

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