Restructure the plot dialog into a style-manager-style master/detail: a
left list of page setups plus a right settings editor. The list shows
<none> (defaults + PDF) and <previous> (the settings the dialog opened
with), then the drawing's layouts (*Model*, *Layout1*, …) and its
standalone named page setups.
- Named page setups live in the ACAD_PLOTSETTINGS dictionary
(src/scene/page_setup.rs: names/get/save/delete/rename, creating the
dictionary if absent); DWG round-trip verified.
- Toolbar New / Copy / Delete | Set current / Preview / Print. Selecting
a row loads it into the editor; Set current writes to the active
layout. Copy duplicates a layout or a setup into a new named setup;
Delete/Rename apply only to named setups.
- Scene::plot_settings_for(name) generalizes effective_plot_settings so
any layout's settings can be loaded; on open the settings are
snapshotted for <previous>.
- Default selection: model space → <none>; a layout → its own setup.
Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>