Add EnergyCalculatorCallback

[efaulhaber]

This PR implements the second version demonstrated in #897:

A cheaper version that evaluates the forces on "fixed" particles only in a callback and then integrates the energy with the explicit Euler method. In my small experiment this added a 6% overhead vs 25% of version 1. It can be made even cheaper by applying the callback only every n steps at the cost of larger time integration errors.

[codecov]

Codecov Report

❌ Patch coverage is 73.80952% with 22 lines in your changes missing coverage. Please review.
✅ Project coverage is 64.70%. Comparing base (433e394) to head (93273d9).

Files with missing lines	Patch %	Lines
src/callbacks/energy_calculator.jl	74.64%	18 Missing ⚠️
test/examples/examples.jl	0.00%	2 Missing ⚠️
src/callbacks/split_integration.jl	0.00%	1 Missing ⚠️
test/callbacks/energy_calculator.jl	66.66%	1 Missing ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##             main     #940      +/-   ##
==========================================
+ Coverage   64.45%   64.70%   +0.25%     
==========================================
  Files         117      119       +2     
  Lines        8122     8203      +81     
==========================================
+ Hits         5235     5308      +73     
- Misses       2887     2895       +8     

Flag	Coverage Δ
unit	64.70% <73.80%> (+0.25%)	⬆️

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[Copilot]

Pull Request Overview

This PR implements the EnergyCalculatorCallback, a second version of energy calculation that evaluates forces on "fixed" (clamped) particles and integrates energy using explicit Euler method. The implementation provides a more efficient alternative to previous energy calculation approaches, adding only ~6% overhead compared to 25% of an earlier version.

• Adds a new EnergyCalculatorCallback for calculating energy contributions from clamped particles in TLSPH systems
• Modifies TotalLagrangianSPHSystem to support energy calculator functionality with new cache allocation
• Updates interaction functions to support selective particle processing for energy calculations

Reviewed Changes

Copilot reviewed 10 out of 10 changed files in this pull request and generated 3 comments.

Show a summary per file

File	Description
src/callbacks/energy_calculator.jl	New callback implementation with energy calculation logic and CombinedMatrix utility
src/schemes/structure/total_lagrangian_sph/system.jl	Added support flag and cache creation for energy calculator functionality
src/schemes/structure/total_lagrangian_sph/rhs.jl	Modified interaction functions to accept custom particle ranges
test/callbacks/energy_calculator.jl	Comprehensive test suite for the new callback
test/examples/examples.jl	Integration test using oscillating beam example
src/TrixiParticles.jl	Export declaration for the new callback
src/callbacks/callbacks.jl	Include statement for new callback file
test/callbacks/callbacks.jl	Include statement for new test file

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