feat(plot): paper catalogue with AutoCAD canonical media names

AutoCAD stores a layout's sheet as the plotter driver's canonical media
name (`ISO_A4_(210.00_x_297.00_MM)`, `ANSI_full_bleed_B_(11.00_x_17.00_Inches)`),
so a drawing saved here has to carry the same spelling for AutoCAD to find
the sheet in its DWG To PDF list, and a name that arrives from AutoCAD must
resolve to its dimensions and go back out untouched.

- New `io::paper_catalog` replaces the eight-entry `paper_sizes`: ISO A/B,
  ANSI, ARCH (incl. E1) and JIS series with full-bleed / expand variants,
  Letter / Legal / Tabloid, millimetre and inch units, a parser that
  reconstructs any well-formed AutoCAD name (custom or driver-specific)
  from its embedded dimensions, driver / legacy-config aliases (`A4`,
  `Letter`, `Ledger`), and dimension matching that prefers the plain sheet.
- The Plot dialog stores the canonical name and shows the sheet as
  `ISO A4 (210 × 297 mm)`; a sheet that only exists in the drawing is
  listed first so it stays selectable.
- A sheet the user did not change keeps the drawing's own media name
  (`paper_name_for_settings`), so a Windows printer's `A4` is not rewritten
  to `ISO_A4_(…)` just by passing through the dialog.
- Drops the unused `PlotFormat` / `PlotOrientation` messages,
  `paper_label_from_dims`, and three duplicated `match "A4" | …` tables.

Tests: catalogue spelling, parser round-trip, aliases, dimension matching,
display formatting, plus dialog ↔ layout round-trips for driver-named,
catalogue and unknown sheets.

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

src/app/mod.rs

@@ -943,8 +943,10 @@ pub(super) struct OpenCADStudio {
     mtext_click_count: u8,
     /// Pending model-space plot window (x0, y0, x1, y1) in world XY, or None.
     plot_window: Option<(f64, f64, f64, f64)>,
-    plot_format: crate::io::paper_sizes::PaperSize,
-    plot_orientation: crate::io::paper_sizes::Orientation,
+    /// Sheet the Plot dialog opens with when the layout has no page setup;
+    /// updated from every plot / apply so the next dialog remembers it.
+    plot_paper: crate::io::paper_catalog::PaperSize,
+    plot_orientation: crate::io::paper_catalog::Orientation,
     /// Backing state for the full Plot / Print dialog.
     plot_dialog: crate::ui::window::plot::PlotDialogState,
     /// Snapshot of the dialog's settings taken when it opened, restored by the
@@ -3317,10 +3319,6 @@ pub enum Message {
     PlotExport,
     /// Callback after the user picks (or cancels) the export path.
     PlotExportPath(Option<std::path::PathBuf>),
-    /// User picked a paper size for the model-space window plot.
-    PlotFormat(crate::io::paper_sizes::PaperSize),
-    /// User picked a sheet orientation for the model-space window plot.
-    PlotOrientation(crate::io::paper_sizes::Orientation),
     /// Export the pending model-space plot window (from PLOTWINDOW) to PDF.
     PlotWindowExport,
     /// Callback after the user picks (or cancels) the window-export path.
@@ -3944,8 +3942,8 @@ impl OpenCADStudio {
             mtext_click_off: 0,
             mtext_click_count: 0,
             plot_window: None,
-            plot_format: crate::io::paper_sizes::PaperSize::A4,
-            plot_orientation: crate::io::paper_sizes::Orientation::Landscape,
+            plot_paper: crate::io::paper_catalog::default_paper().clone(),
+            plot_orientation: crate::io::paper_catalog::Orientation::Landscape,
             plot_dialog: crate::ui::window::plot::PlotDialogState::default(),
             plot_prev: None,
             plot_setup_template: None,