Layouts: a viewport on first opening (LAYOUTCREATEVIEWPORT)

A layout opened for the first time - one whose sheet viewport had to be
made, or one created in this session - gets a viewport centred on the
printable area, 0.8 of its width and height, zoomed to the model's
extents, while LAYOUTCREATEVIEWPORT is on. The profile variable takes
ON/OFF or 1/0 and is kept with the settings.

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>

src/app/commands/mod.rs

@@ -712,6 +712,7 @@ inventory::submit!(crate::command::CommandRegistration {
         "UOSNAP",
         "FIELDDISPLAY",
         "SURFACEASSOCIATIVITY",
+        "LAYOUTCREATEVIEWPORT",
         "FIELDEVAL",
         "PDFIMPORTMODE",
         "PDFIMPORTFILTER",