Implement Sugiyama

[BjarkeHautop]

Implements Sugiyama layout based on the Rust implementation https://github.com/paddison/rust-sugiyama. Also ports several fixture tests to
verify they give the same output as the source.

The algorithm needs to mutate the graph, so added the needed graph operations to Sugiyama.

Also fixed a bug in the reference implementation: mark_type_1_conflicts
runs before vertex positions are populated there, so its conflict detection is
a no-op, see paddison/rust-sugiyama#26 and paddison/rust-sugiyama#27.

Generated with the help of Claude Code, and manually modified and verified.

Fixes #20

[codecov]

Codecov Report

❌ Patch coverage is 97.51553% with 20 lines in your changes missing coverage. Please review.
✅ Project coverage is 97.47%. Comparing base (0bfd2ed) to head (53ede03).
⚠️ Report is 15 commits behind head on master.

Files with missing lines	Patch %	Lines
src/sugiyama/ordering.jl	92.72%	12 Missing ⚠️
src/sugiyama/coordinates.jl	96.21%	7 Missing ⚠️
src/sugiyama/ranking.jl	99.62%	1 Missing ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##           master     #100      +/-   ##
==========================================
+ Coverage   97.40%   97.47%   +0.06%     
==========================================
  Files          10       16       +6     
  Lines         579     1384     +805     
==========================================
+ Hits          564     1349     +785     
- Misses         15       35      +20     

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