M4.20: Document Setup with bleed, transparency grid, paper and type options

File > Document Setup is a tabbed dialog over one engine command,
document.setup (no params: a query; any keys: one undo step;
document.setUnits stays as the units alias).

- General: units, bleed (four sides with a link toggle), Edit Artboards,
  Show Images in Outline Mode (greyscale pixels under the frame),
  Highlight Substituted Fonts/Glyphs (pink boxes on screen only).
- Transparency: grid size and colour presets or custom colours, Simulate
  Colored Paper, the flattener preset (built-in or saved) and Discard
  White Overprint (Overprint Preview keeps white overprints visible).
- Type: language with its quotes, Use Typographer's Quotes for the Type
  tool and Smart Punctuation, superscript/subscript size and position and
  small caps size (Character panel position/smallCaps; changing the
  setup restyles the text in the same undo step), text export (SVG text
  as text or outlines by default).
- The canvas draws a red bleed outline and the grid in the document's
  colours and cell size as one textured quad, also in rotated views; a
  white Background Contents exports raster formats opaque.

Model: Document.setup (DocSetup, defaulted, skipped when default) and
CharStyle position/small_caps; old files load unchanged.
tests_transparencygrid's helper now finds the grid by its texture (the
grid is one textured mesh instead of per-cell rectangles).

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>

crates/text/src/tests_scripts.rs

@@ -0,0 +1,50 @@
+//! Superscript, subscript and synthesized small caps (Character panel, Document Setup → Type).
+
+use kurbo::Shape;
+use vectorcraft_doc::{CharPosition, CharStyle, ScriptMetrics, TextObject};
+
+use super::*;
+
+fn layout_of(text: &str, st: CharStyle) -> TextLayout {
+    layout(FontDb::global(), &TextObject::point(kurbo::Point::ZERO, text, st))
+}
+
+fn glyph_box(l: &TextLayout, i: usize) -> kurbo::Rect {
+    l.glyphs[i].outline.bounding_box()
+}
+
+#[test]
+fn superscript_and_subscript_scale_and_shift_glyphs() {
+    let base = CharStyle { size: 20.0, ..CharStyle::default() };
+    let normal = layout_of("H", base.clone());
+    let m = ScriptMetrics { size: 50.0, position: 40.0 };
+    let sup = layout_of("H", CharStyle { position: CharPosition::Superscript(m), ..base.clone() });
+    let sub = layout_of("H", CharStyle { position: CharPosition::Subscript(m), ..base.clone() });
+    let (n, p, b) = (glyph_box(&normal, 0), glyph_box(&sup, 0), glyph_box(&sub, 0));
+    // Half the height and advance.
+    assert!((p.height() - n.height() * 0.5).abs() < 0.05, "{p:?} vs {n:?}");
+    assert!((sup.glyphs[0].advance - normal.glyphs[0].advance * 0.5).abs() < 1e-6);
+    // Raised / lowered by 40% of 20 pt (y points down).
+    assert!((p.y1 - (n.y1 - 8.0)).abs() < 0.05, "{p:?}");
+    assert!((b.y1 - (n.y1 + 8.0)).abs() < 0.05, "{b:?}");
+    // Line metrics keep the full size.
+    assert_eq!(sup.lines[0].ascent, normal.lines[0].ascent);
+}
+
+#[test]
+fn small_caps_draw_lowercase_as_smaller_capitals() {
+    let base = CharStyle { size: 20.0, ..CharStyle::default() };
+    let cap = layout_of("A", base.clone());
+    let cap14 = layout_of("A", CharStyle { size: 14.0, ..base.clone() });
+    let small = layout_of("Aa", CharStyle { small_caps: Some(70.0), ..base.clone() });
+    // The capital is unchanged; the lowercase letter is a capital A at 70% (14 pt).
+    assert_eq!(small.glyphs[0].advance, cap.glyphs[0].advance);
+    assert!((small.glyphs[1].advance - cap14.glyphs[0].advance).abs() < 1e-6);
+    let (a, s) = (glyph_box(&cap14, 0), glyph_box(&small, 1));
+    assert!((s.height() - a.height()).abs() < 0.05, "{s:?} vs {a:?}");
+    // Byte offsets still map back to the source characters.
+    assert_eq!((small.glyphs[1].byte, small.glyphs[1].len), (1, 1));
+    // All Caps wins over Small Caps.
+    let all = layout_of("a", CharStyle { all_caps: true, small_caps: Some(70.0), ..base });
+    assert_eq!(all.glyphs[0].advance, cap.glyphs[0].advance);
+}