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 <noreply@anthropic.com>

src/ui/style/form.rs

@@ -189,18 +189,25 @@ pub fn labeled_field_enabled<'a>(
     .into()
 }
 
-/// A short unlabeled text field for a compact multi-value row (`L B R T`).
-pub fn compact_field<'a>(
-    placeholder: &'a str,
+/// A `label : text field` pair with its own label width, for rows that put
+/// several small values side by side.
+pub fn labeled_field_compact<'a>(
+    label: Cow<'static, str>,
     value: &'a str,
     on_input: impl Fn(String) -> Message + 'a,
-    width: f32,
+    label_width: f32,
+    field_width: f32,
 ) -> Element<'a, Message> {
-    text_input(placeholder, value)
-        .on_input(on_input)
-        .style(field_style)
-        .size(12)
-        .padding([3, 6])
-        .width(width)
-        .into()
+    row![
+        text(label).size(11).style(muted_style).width(label_width),
+        text_input("", value)
+            .on_input(on_input)
+            .style(field_style)
+            .size(12)
+            .padding([3, 6])
+            .width(field_width),
+    ]
+    .spacing(6)
+    .align_y(iced::Center)
+    .into()
 }