fix(pdfshxtext): reference grouping, object share, wider glyph set, drawing-order import

Text blocks join side by side or stacked within two heights; oversized
shapes join no group; the group share counts selected objects; Latin-1,
Latin Extended, Greek, Cyrillic and the diameter sign are compared from
the font's own glyphs with look-alikes resolved to the lowest code; a lone
circle reads 0; MTEXT direction is by style. PDFIMPORT keeps drawing order.

Co-Authored-By: Claude Opus 5.5 <[email protected]>

src/app/commands/pdf_shx_text.rs

@@ -288,6 +288,7 @@ impl OpenCADStudio {
             mtext.height = line.height;
             mtext.rectangle_width = 0.0;
             mtext.attachment_point = codec::entities::AttachmentPoint::BottomLeft;
+            mtext.drawing_direction = codec::entities::DrawingDirection::ByStyle;
             mtext.style = line.font;
             mtext.common.layer = if settings.current_layer {
                 current_layer.clone()