feat(attedit): enhanced attribute editor with 3 tabs

Grow the attribute editor into a three-tab enhanced editor:
- Attribute: the tag/prompt/value list; click a row to select it, edit
  its value below.
- Text Options: the selected attribute's Text Style, Justification,
  Height, Rotation, Width Factor, Oblique Angle, Backwards, Upside down.
- Properties: the selected attribute's Layer, Linetype, Color,
  Lineweight (the colour list also surfaces a non-standard current
  colour so it displays and round-trips).

Applying writes value, text-formatting and common-property edits back to
each attribute positionally (guarded on block name + count), with undo
and a repaint. OK/Cancel are replaced by a single Apply button in a top
toolbar that commits but keeps the dialog open, matching the other modal
windows — the frame ✕ closes and discards un-applied edits. The frame
adopts the shared style-window palette, tab styling and sizing.

Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>

src/app/view/mod.rs

@@ -1363,7 +1363,7 @@ impl OpenCADStudio {
             OverwriteWarning => (420, 180),
             SaveDialog => (560, 480),
             PointStyle => (360, 470),
-            AttributeEditor => (460, 440),
+            AttributeEditor => (640, 500),
         };
         Some((w as f32 + EXTRA_W, h as f32 + EXTRA_H))
     }