feat(plot): printer driver properties and a roomier plot dialog

Properties… next to the printer used to open the CUPS web interface in a
browser. It now edits the driver options of the *selected* printer the
way LibreOffice's Properties… does, without leaving the plot dialog:

- CUPS platforms (Linux, any desktop; macOS): an in-line editor lists the
  printer's PPD options as `lpoptions -l` reports them — media type,
  colour mode, quality, duplex, trays, scaling — with readable choice
  labels, Reset / Cancel / Apply. Apply keeps only the choices that differ
  from the driver defaults, per printer, in the plot config, and every job
  for that printer passes them as `lp -o key=value`. Where CUPS cannot
  answer, the desktop's printer settings panel opens instead of a browser.
- Windows: the driver's document-properties sheet (`DocumentPropertiesW`
  with prompt, owned by the main window) and, on OK, the result stored as
  the user's printing preferences for that printer (`SetPrinter` level 9),
  which the job honours. `printui /e` (printing preferences) replaces the
  device-properties sheet as the fallback.

The desktop print portal was tried first and dropped: GTK 4's print
dialog loses the preselected printer when the default queue is listed
before it, so the dialog always opened on the wrong printer.

Dialog layout: the modal grows to 940×620; Printer / plotter and Paper
size share a line with their pickers (long queue and media names now fit);
Copies + Properties… and Custom… sit beneath; the custom-sheet editor
labels each margin (Left / Right, Top / Bottom) and shows the unit.

Also recognises `none_device`, AutoCAD's stored spelling for "no plotter",
and writes it back unchanged.

Tests: `lpoptions` parsing and keyword humanising, the editor flow (load,
stale answer ignored, set, apply, remember, reset, error, cancel), device
name round-trips including `none_device`.

Co-Authored-By: Claude Opus 5 <[email protected]>

src/app/view/modal.rs

@@ -64,8 +64,8 @@ impl OpenCADStudio {
     ) -> Element<'s, Message> {
         sized_flow(
             extra,
-            760,
-            540,
+            940,
+            620,
             |flow| {
                 crate::ui::window::plot::view_window(
                     &self.plot_dialog,