Two world_offset bugs in viewport rendering.
(1) Solid3D / Region / Body meshes were tessellated straight out of
the ACIS SAT data in WCS, while the wire / hatch / face3d pipelines
all run in `(WCS - world_offset)` local space. At UTM scale the
result was triangles drifting millions of units off-camera every
frame. `offset_mesh_lod_set` post-processes the freshly built
`MeshLodSet`, subtracting `world_offset` from every vertex and
recomputing `world_aabb` so the LOD / cull math agrees with the
shared camera space. Applied at the three `tessellate_volume`
call sites — load, `add_entity`, and `populate_meshes_from_document`.
(2) Paper-space content viewports rendered blank on UTM drawings.
The DWG / DXF saved `view_target = (0, 0, 0)` while the model sat
around `world_offset`; the CPU projection in `viewport_content_wires`
already had a "saved view doesn't overlap content cluster →
auto-fit to (world_offset ± local_extent_max)" fallback, but the
GPU path read `vp.view_target` literally and culled every entity
against the empty WCS rect. `camera_for_viewport` now applies the
same overlap test + auto-fit, and `model_wires_for_viewport`
derives its frustum AABB / wpp from the resulting camera so both
the camera and the cull agree on which area to show.
Folding `view_center` directly into `effective_target_wcs` matches
the CPU path's `display_center_x = view_target + view_center`,
removing the prior `+ view_right * view_center.x` shift that would
double-count once auto-fit had overwritten the target.
74a685d0e8