- Add `active_ucs: Option<Ucs>` per-tab state to DocumentTab
- Add `ucs_to_wcs`, `wcs_to_ucs`, `ucs_z_axis`, `ucs_rotated_z` helpers
- Add `Camera::pick_on_plane` for ray–plane intersection against any plane
- Mouse picks project onto the active UCS XY plane instead of world XY
- Typed coordinates are converted from UCS space to WCS before dispatch
- UCS command now really activates/deactivates a UCS:
- `UCS W` resets to WCS (clears active_ucs)
- `UCS <name>` activates a named UCS
- `UCS SAVE <name>` saves the current active UCS
- `UCS ORIGIN x,y,z` shifts origin (in current UCS space)
- `UCS X/Y/Z <angle>` rotates the UCS around its own axes
Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>
- Add active_viewport: Option<Handle> field to Scene
- Add EnterViewport(Handle) and ExitViewport messages
- Double-click on a user viewport (id > 1) enters MSPACE;
double-click on empty area while in MSPACE exits to PSPACE
- MSPACE middle-drag pans the viewport's model-space view (view_target)
- MSPACE scroll zooms the viewport's view_height / custom_scale
- Drawing commands inside MSPACE receive model-space coordinates
via paper_to_model() coordinate transform
- Active viewport rendered with yellow dashed border (vs. cyan solid)
- Camera screen_delta_to_world helper for MSPACE pan conversion
- LayoutSwitch clears active_viewport
Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>
