jetls fixes

[BjarkeHautop]

Various fixes for issues found by jetls, such as

• using isnothing over == nothing.
• explicit === over ∈, since ∈ can return missing, whereas === on Symbols always returns a Bool.
• @addcall generated align(g; kwargs...) = layout(Align(; kwargs...), g), but Align has no all-keyword constructor.
• SquareGrid skip-list check now uses a Set instead of Vector, avoiding the same missing-prone ∈.
• Stress uses any(isinf, distances) instead of any(isequal(typemax(FT)), distances).
• replaced for i in 1:length(x)/1:size(x, 1) loops with eachindex/axes.

[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 97.41%. Comparing base (0bfd2ed) to head (6ad1e2f).
⚠️ Report is 15 commits behind head on master.

Additional details and impacted files

@@           Coverage Diff           @@
##           master      #99   +/-   ##
=======================================
  Coverage   97.40%   97.41%           
=======================================
  Files          10       10           
  Lines         579      580    +1     
=======================================
+ Hits          564      565    +1     
  Misses         15       15           

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