Each model-space tile now carries its own visual style instead of one
global mode shared by every pane:
- ModelTile gains a `render_mode`; the active tile renders with the live
picker mode, inactive tiles keep their stored style, so changing one
tile no longer changes the others. Split inherits the source style.
- SetRenderMode writes only the active tile; switching the active tile
mirrors its style back into the tab (picker + live render).
- Persisted through the *Active VPORT entries (acadrust now round-trips
the render mode via DXF code 281 / DWG RC 281), restored on open for
both tiled and single-tile model layouts.
- Bump acadrust to pick up the VPORT render-mode field.
Co-Authored-By: Claude Opus 4.8 <[email protected]>