Add normal computation and Jacobian methods for collision candidates

[zfergus]

Description

• Implemented compute_normal and compute_normal_jacobian methods for various collision candidates

Type of change

• Enhancement (non-breaking change which improves existing functionality)

How Has This Been Tested?

• Added unit tests for normal computation in test_normals.cpp

[Copilot]

Pull Request Overview

This pull request adds normal computation and Jacobian methods for various collision candidates in an IPC (Incremental Potential Contact) library. The implementation provides standardized normal vector calculation capabilities across different collision stencil types.

Key Changes:

• Added compute_normal and compute_normal_jacobian methods to the base CollisionStencil class
• Implemented these methods for all collision candidate types (vertex-vertex, edge-vertex, edge-edge, face-vertex, and plane-vertex)
• Added comprehensive unit tests with finite difference validation for all collision types

Reviewed Changes

Copilot reviewed 14 out of 14 changed files in this pull request and generated 7 comments.

Show a summary per file

File	Description
src/ipc/candidates/collision_stencil.hpp	Added public interface methods and protected virtual methods for normal computation
src/ipc/candidates/collision_stencil.cpp	Implemented base normal computation logic with normalization and optional flipping
src/ipc/candidates/*.hpp	Added protected method declarations for each collision candidate type
src/ipc/candidates/*.cpp	Implemented candidate-specific normal computation methods
tests/src/tests/candidates/test_normals.cpp	Added comprehensive unit tests for all collision types
tests/src/tests/candidates/CMakeLists.txt	Added new test file to build system

[codecov]

Codecov Report

Attention: Patch coverage is 99.00000% with 1 line in your changes missing coverage. Please review.

Project coverage is 96.24%. Comparing base (6895dda) to head (2af11ce).
Report is 1 commits behind head on main.

Files with missing lines	Patch %	Lines
src/ipc/candidates/collision_stencil.cpp	95.65%	1 Missing ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##             main     #182      +/-   ##
==========================================
- Coverage   96.36%   96.24%   -0.13%     
==========================================
  Files         103      104       +1     
  Lines        7878     7991     +113     
==========================================
+ Hits         7592     7691      +99     
- Misses        286      300      +14     

Flag	Coverage Δ
unittests	96.24% <99.00%> (-0.13%)	⬇️

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