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>

Cargo.toml

@@ -63,7 +63,7 @@ naga = { version = "27", features = ["wgsl-in"] }
 
 [target.'cfg(target_os = "windows")'.dependencies]
 libloading = "0.8"
-windows-sys = { version = "0.61", features = ["Win32_UI_Shell", "Win32_UI_WindowsAndMessaging", "Win32_UI_Input", "Win32_System_LibraryLoader", "Win32_System_Threading", "Win32_Security", "Win32_System_Com", "Win32_System_Registry", "Win32_Storage_FileSystem", "Win32_Foundation", "Win32_Graphics_Printing"] }
+windows-sys = { version = "0.61", features = ["Win32_UI_Shell", "Win32_UI_WindowsAndMessaging", "Win32_UI_Input", "Win32_System_LibraryLoader", "Win32_System_Threading", "Win32_Security", "Win32_System_Com", "Win32_System_Registry", "Win32_Storage_FileSystem", "Win32_Foundation", "Win32_Graphics_Printing", "Win32_Graphics_Gdi"] }
 
 [target.'cfg(target_os = "linux")'.dependencies]
 ashpd = { version = "0.13.13", default-features = false, features = ["async-io", "wayland"] }