Fix ForceAtlas2 random cell ordering by sort positions by vertex in draw_graph function

[LouisFaure]

Hi, I noticed that tl.draw_graph was completely scrambling the order of the cells in the FA2 embedding, it seems that this is resolved by adding this line of code!

Tested on
cugraph: 26.02.00
rapdis_singlecell: 0.15.0rc4

Cheers

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No actionable comments were generated in the recent review. 🎉

ℹ️ Recent review info

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Run ID: ea4fd5f8-839d-426d-8ad0-dc178a657cdf

📥 Commits

Reviewing files that changed from the base of the PR and between 67eccb7 and d6b9f58.

📒 Files selected for processing (1)

• docs/release-notes/0.15.0.md

✅ Files skipped from review due to trivial changes (1)

• docs/release-notes/0.15.0.md

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📝 Walkthrough

Summary by CodeRabbit

• Bug Fixes
  • Fixed a non-deterministic ordering in graph layout coordinates so output positions are consistently ordered and reproducible across runs, ensuring stable layouts and reliable downstream analyses.

Walkthrough

After computing positions with force_atlas2, the code now sorts the positions dataframe by the "vertex" column and resets its index before stacking "x" and "y" into the final layout, ensuring deterministic ordering by ascending vertex id.

Changes

Cohort / File(s)	Summary
Draw Graph Vertex Ordering src/rapids_singlecell/tools/_draw_graph.py	Sort positions by "vertex" and reset index after force_atlas2 so output layout rows align with ascending vertex ids.
Release Notes docs/release-notes/0.15.0.md	Added bug-fix note documenting deterministic ordering fix for tl.draw_graph / ForceAtlas2 output.

Estimated code review effort

🎯 2 (Simple) | ⏱️ ~10 minutes

🚥 Pre-merge checks | ✅ 3

✅ Passed checks (3 passed)

Check name	Status	Explanation
Title check	✅ Passed	The title clearly and specifically describes the main change: sorting positions by vertex to fix random cell ordering in the draw_graph function's ForceAtlas2 output.
Description check	✅ Passed	The description is directly related to the changeset, explaining the observed issue with cell ordering in draw_graph and indicating the fix was tested.
Docstring Coverage	✅ Passed	Docstring coverage is 100.00% which is sufficient. The required threshold is 80.00%.

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🧪 Generate unit tests (beta)

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[Intron7]

Can you add a release note?

[codecov-commenter]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 87.75%. Comparing base (51817a0) to head (d6b9f58).
⚠️ Report is 1 commits behind head on main.

Additional details and impacted files

@@           Coverage Diff           @@
##             main     #621   +/-   ##
=======================================
  Coverage   87.75%   87.75%           
=======================================
  Files          96       96           
  Lines        6996     6997    +1     
=======================================
+ Hits         6139     6140    +1     
  Misses        857      857           

Files with missing lines	Coverage Δ
src/rapids_singlecell/tools/_draw_graph.py	97.29% <100.00%> (+0.07%)	⬆️