Multi-patch coupling support

[Crazy-Rich-Meghan]

Feature added:

• Multi-patch support for the gsLookupFunction.h
• Multi-patch version of the perpendicular flap

[Copilot]

Pull Request Overview

This PR introduces multi-patch support to the lookup function API and updates the perpendicular-flap example to use the new functionality.

• Added a gsLookupFunction wrapper class managing multiple gsLookupFunctionSingle instances
• Renamed and refactored the original gsLookupFunction to gsLookupFunctionSingle, adjusting storage and warnings
• Updated the perpendicular-flap example to build and use a multi-patch lookup function for stress data

Reviewed Changes

Copilot reviewed 2 out of 2 changed files in this pull request and generated 1 comment.

File	Description
gsLookupFunction.h	Added multipatch wrapper class, refactored single-patch lookup into gsLookupFunctionSingle
examples/perpendicular-flap-multipatch-vertex-gismo.cpp	New example using multi-patch lookup and updated coupling logic

Comments suppressed due to low confidence (3)

examples/perpendicular-flap-multipatch-vertex-gismo.cpp:1

• The @file annotation doesn’t match this filename; update it to perpendicular-flap-multipatch-vertex-gismo.cpp to avoid confusion.

/** @file solid-gismo-elasticity.cpp

gsLookupFunction.h:92

• [nitpick] This override always throws an error advising to use the patch-specific overload; consider marking these no-ops as = delete to prevent accidental misuse.

    void eval_into(const gsMatrix<T>& u, gsMatrix<T>& result) const override

gsLookupFunction.h:40

• [nitpick] No unit tests cover the new multi-patch lookup functionality; adding tests for construction, add/set, and evaluation across patches would improve reliability.

    gsLookupFunction(size_t nPatches = 0)