fix(region,clenshaw): drop redundant >= 1 + break in unsigned loop (CodeQL #3512)

[ibell]

Summary

Follow-up to merged PR #2914 that addresses the one outstanding
review note (CodeQL alert #3512):

src/Region/PiecewiseChebyshevCurve.cpp:57
Comparison result is always the same
Comparison is always true because k >= 1.

The Clenshaw recurrence iterates k = N down to 1 inclusive. The
original code used for (std::size_t k = N; k >= 1; --k) with an
inner if (k == 1) break; to dodge unsigned underflow. CodeQL
correctly noted that k >= 1 is always true for unsigned k --
the break is the real loop exit, not the condition.

Canonical fix: for (std::size_t k = N; k > 0; --k). Iterates k =
N, N-1, ..., 1, exits cleanly before k = 0 would happen. Same
semantics, same generated code, CodeQL happy.

All other actionable review items on #2914 were already addressed
in commits during that PR (the coderabbit review thread shows ✅
markers on 12 of 13 comments); this one slipped through because it
was a separate CodeQL alert, not a coderabbit suggestion.

Test plan

• ./build_catch/CatchTestRunner "[Region][boundary_curve_cheb]" -- 404 assertions / 4 test cases pass
• CI green (CodeQL re-scan)

🤖 Generated with Claude Code

Summary by CodeRabbit

• Refactor
  • Improved loop condition logic in mathematical computation to enhance code clarity and maintainability while preserving existing functionality.

[coderabbitai]

Caution

Review failed

The pull request is closed.

ℹ️ Recent review info

⚙️ Run configuration

Configuration used: Organization UI

Review profile: CHILL

Plan: Pro Plus

Run ID: d5e87a21-0904-4fc8-acdb-d9e34ea4d686

📥 Commits

Reviewing files that changed from the base of the PR and between 1ad24fa and edb9d72.

📒 Files selected for processing (1)

• src/Region/PiecewiseChebyshevCurve.cpp

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📝 Walkthrough

Walkthrough

Loop condition in the clenshaw_eval function refactored from an unsigned k >= 1 guard with an explicit k == 1 break to a simpler k > 0 condition. The iteration range remains unchanged, iterating backward from N to 1.

Changes

Clenshaw Evaluation Loop Optimization

Layer / File(s)	Summary
Clenshaw Loop Condition Simplification src/Region/PiecewiseChebyshevCurve.cpp	Loop condition changed from k >= 1 with explicit k == 1 break to k > 0, eliminating the special case while maintaining the same iteration range from N down to 1.

Poem

I hopped through code beneath the moonlight,
Tidied a loop to make its steps right.
From k >= 1 with a break so terse,
To k > 0 — the same path, less terse. 🐇✨

✨ Finishing Touches

📝 Generate docstrings

• Create stacked PR
• Commit on current branch

🧪 Generate unit tests (beta)

• Create PR with unit tests
• Commit unit tests in branch ihb/svd-codeql-clenshaw-loop

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