fix(print): send Windows plots to the chosen printer, name the default, report failures

On Windows a plot with no printer chosen went to the PDF application's
bare "print" verb — whatever that application considered its default —
and a viewer without a "printto" verb (Edge, store readers) silently
dropped the printer the dialog had chosen. The dialog also never named the
system default, and a failed printer enumeration left only "Default" and
"PDF" with the reason written to a console nobody sees.

- The default printer is looked up by name (GetDefaultPrinterW) both for
  the dialog's "System default printer (…)" entry and before every job.
- A pure route decision (plan_print_route) resolves "Default" to that
  name and uses the PDF application only when it registered a "printto"
  verb for .pdf (AssocQueryStringW); otherwise the job goes straight to
  the spooler through the existing GDI path. The report says which:
  "Sent to printer: NAME (direct print | via the PDF application)".
- list_printers reports the system's own error; the plot dialog shows it
  under the printer row and the command line warns once. A desktop without
  CUPS is an empty list, not an error.
- PRINTERS command: default printer, listed printers (or the error) and,
  on Windows, the print route — a report to paste into an issue.
- Properties… on the Default entry opens that printer's preferences sheet.
- GDI path: the driver's dmSize is kept (its private data lives behind
  it), the print raster is no longer memoised for the session, and a
  spooled temporary PDF is removed.

Tests: route planning (named / blank / no default / printto or not), the
PRINTERS command; the two Windows-only GDI tests pass the resolved name.

Co-Authored-By: Claude Opus 5 <noreply@anthropic.com>

src/locale_catalog.rs

@@ -3144,6 +3144,15 @@ pub(super) fn message_attribute(source: &str) -> Option<(&'static str, &'static
         "World" => Some(("common", "world")),
         "Write Block" => Some(("insert", "write-block")),
         "X (mm)" => Some(("plot", "x-mm")),
+        "Default printer: {name}" => Some(("plot", "default-printer-name")),
+        "Default printer: none reported by the system" => Some(("plot", "default-printer-none-reported-by-the-system")),
+        "Printers: none listed by the system" => Some(("plot", "printers-none-listed-by-the-system")),
+        "Printers ({count}):" => Some(("plot", "printers-count")),
+        "Could not list printers: {error}" => Some(("plot", "could-not-list-printers-error")),
+        "Plots go through the PDF application: {command}" => Some(("plot", "plots-go-through-the-pdf-application-command")),
+        "Plots go straight to the printer (no PDF application registers a print verb)." => Some(("plot", "plots-go-straight-to-the-printer-no-pdf-application-registers-a-print-verb")),
+        "via the PDF application" => Some(("plot", "via-the-pdf-application")),
+        "direct print" => Some(("plot", "direct-print")),
         "X = %{x},  Y = %{y},  Z = %{z}" => Some(("inquiry", "x-x-y-y-z-z")),
         "X Scale" => Some(("properties", "x-scale")),
         "X-Ray" => Some(("draw", "x-ray")),