cad/openvsp: Update to 3.49.0

ChangeLog:
https://openvsp.org/blogs/announcements/2026/04/03/openvsp-3-49-0-released

Features:

• Stowed / Retracted landing gear
• TRA Clearance model
• Single gear auxiliary geometry
• Faster interactivity with landing gear

Build system:

• Use venv when building Ubuntu to fix numpy version problems
• Update to Eigen3 5.0.0
• Update OpenABF to support new Eigen

Fixes:

• Center of rotation with ABS positioning fixed
• Wave drag crash on load
• Ambiguous subsurface with line subsurfaces in WaveDrag
• Fix mismatch of gear plane for certain analyses
• Improve robustness of corner rounding
• Fix crash with ground maneuverability analysis
• Fix scrolling stability of Check Box Browsers
• Fix some Python unit tests
• Only show ‘Apply Rotation’ when it makes sense
• Fix landing gear scaling on second load
• Fix crash due to non-deregistered attribute collection