FP-20: Ceiling Shapes (Vaults, Slopes, Polygons)

[steilerDev]

As a homeowner, I want to define ceiling shapes beyond flat so that I can document vaulted, sloped, and custom ceiling geometries.

Parent Epic: #752 (EPIC-16: Floor Plans & Utility Tracking)
Priority: Could Have
Phase: 5 — Multi-Floor & Special Structures

Acceptance Criteria

• 1. The ceiling surface page includes a "Shape" editor section above the layer stack
• 2. Shape types are selectable: flat, barrel_vault, groin_vault, sloped, polygon, custom
• 3. barrel_vault shape has adjustable parameters: apex_height_mm, span direction (reference wall)
• 4. groin_vault shape has adjustable parameters: apex_height_mm (vault peak above spring line)
• 5. sloped shape has adjustable parameters: min_height_mm, max_height_mm, slope_angle_degrees, reference_wall_id
• 6. polygon shape allows defining an arbitrary cross-section profile via vertex editing
• 7. custom shape allows free-form profile path editing using bezier curves
• 8. Each shape renders an SVG profile curve in the cross-section view showing the ceiling shape above the layer stack
• 9. Reference wall selection is available for sloped and vaulted shapes (dropdown of walls on the current floor)
• 10. Shape parameters are stored via the PUT /api/floor-plans/floors/:floorId/ceiling-shape endpoint as JSON
• 11. Preset shapes (barrel_vault, groin_vault, sloped) show a preview with reasonable defaults before parameter adjustment
• 12. Switching shape type resets parameters to defaults for the new type (with confirmation if parameters were customized)

Notes

• Dependencies: FP-12 (FP-12: Ceiling & Floor Surface Layers #764) — ceiling surface view must exist
• This extends the basic ceiling shape rendering from FP-12 with full editing capabilities
• The profile curve is 2D (cross-section), not 3D — it shows the ceiling shape as seen from a side view