Feat: Viewport orientation gizmo with XYZ/ABCD toggle

[arossti]

Summary

• New viewport orientation gizmo — 2D canvas overlay in top-right corner showing camera orientation
• Two modes: XYZ (Cartesian 3 axes) and ABCD (Quadray tetrahedral 4 axes), toggled by clicking the mode label
• Click any axis bubble to snap the camera to that view
• Louis Trümpler (ifc5cad) attribution added for ViewGizmo inspiration

Changes

• modules/rt-gizmo.js — New self-contained gizmo module (canvas overlay, axis projection, interaction)
• modules/rt-rendering.js — Wire gizmo into scene init and animation loop; expose mode API
• modules/rt-delta.js — Add "gizmo-mode" to view delta system for save/load
• LICENSE / README.md — Third-party attribution for Louis Trümpler / ifc5cad

Test plan

• Gizmo appears top-right, axes rotate in sync with camera orbit
• XYZ mode: 3 primary + 3 secondary bubbles with correct colors
• ABCD mode: 4 primary + 4 secondary bubbles with tetrahedral directions
• Click-to-snap: X → side view, Z → top view, A/B/C/D → tet vertex views
• Mode toggle persists across view save/load
• No interference with orbit/pan/zoom on main canvas

🤖 Generated with Claude Code

Co-Authored-By: Andy🤦‍♂️ & Claude🤖 andy@openbuilding.ca

[github-actions]

🤖 Claude Code Review

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