Refactor testing methodology to match Math_Foundations approach

[AronT-TLV]

Summary

Successfully refactored Linear_Algebra testing methodology to align with the superior Math_Foundations three-tier testing approach, ensuring mathematical correctness is never compromised by visualization failures.

Key Changes

1. Module-Level Environment Detection

• Added CI/headless environment detection to src/Linear_Algebra.jl
• Automatic plotting configuration (headless vs interactive)
• Matches Math_Foundations pattern exactly

2. Three-Tier Testing Strategy

• Pure Computational Functions: calculate_* functions with NO try-catch
• Integration Tests: Plotting functions with selective error handling
• Legacy Compatibility: Maintain backward compatibility

3. Modular Test Structure

• Split monolithic runtests.jl into modular structure
• Created test_linear_algebra_basic.jl and test_linear_algebra_transform.jl
• Clean separation of concerns

4. Function Separation

• Added calculate_param_line() as pure computational function
• Refactored plot_param_line() to use computational core
• Fixed Point2f type consistency in center_of_gravity

5. Enhanced Error Handling

• Computational errors always fail tests (no try-catch)
• Only catch display/plotting errors ("display", "GKS", ArgumentError)
• Re-throw computational errors to ensure mathematical accuracy

6. Updated Documentation

• Comprehensive updates to .github/copilot-instructions.md
• Added new testing methodology sections
• Added Julia compilation patience notes
• Updated function signatures with new computational functions

Test Results

• ✅ All 68 tests passing consistently
• ✅ ~16 second execution time
• ✅ Mathematical accuracy preserved
• ✅ CI compatibility ensured
• ✅ Backward compatibility maintained

Architecture Improvements

• Robust separation of computational logic from visualization
• Environment-aware module loading
• Consistent type handling (Point2f)
• Comprehensive test coverage without compromising mathematical rigor

This refactor brings Linear_Algebra up to the same standard as Math_Foundations while maintaining all existing functionality and improving test reliability.