feat(plot): QUICKPRINT/QP — plot a selection's bounding box to PDF (#325)

Run QUICKPRINT (or QP), select objects, then Enter: the selection's
bounding box becomes the plot window and a PDF is written next to the
drawing (<name>_<timestamp>.pdf) using the active page setup, with no
dialog. Model space.

Implemented as a selection-gathering CadCommand (src/modules/view/
quick_print.rs) returning CmdResult::QuickPrint(handles); the host
(on_quick_print_handles) unions the picked entities' AABBs, sets the
plot window, and reuses the tested clipped window-export path.

Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>

src/modules/view/mod.rs

@@ -9,6 +9,7 @@ mod ortho;
 mod pan;
 mod persp;
 pub mod plot_window;
+pub mod quick_print;
 mod properties_palette;
 mod sheetset;
 mod solid;