fix(dim): draw a dimension from the picture it carries

A DIMENSION references the block "that contains the entities that make up
the dimension picture", and that block is the picture: AutoCAD requires
it and draws it, BricsCAD draws it when present and only renders from the
dimension variables when it is missing. OCS re-derived the picture from
DIMVARS every time and ignored the block entirely.

That works while a style agrees with what the drawing actually drew. A
Revit-exported schedule here does not: its style stores DIMTXT already in
drawing units beside a DIMSCALE meant to scale it, so the text came out
three hundred times too tall, and each dimension carries a DIMFXL
override that is likewise already in drawing units, so the extension
lines ran nearly a million units past the points they measure.

Neither is guesswork about units now. The block holds the geometry the
drawing was authored with, so it is drawn: the contents are already in
world space and the block's base point is the origin, and the identity
instance that carries them exists only to reuse the scene graph's
ByBlock / layer-0 colour resolution. Every wire answers to the dimension,
so a pick still selects the dimension rather than one of its pieces.
Re-deriving stays as the fallback for a dimension with no block.

Annotative dimensions keep the old path: their several representations
are separate blocks and choosing between them is what the annotation
machinery already does, while the doctrine above assumes one picture.

A picture is only good while its inputs hold, so it is dropped when they
change: editing a dimension's properties, and saving the dimension style
it is drawn with. Entity edits already dropped it.

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

src/app/properties.rs

@@ -1828,6 +1828,16 @@ impl OpenCADStudio {
     pub(super) fn invalidate_property_targets(&mut self, i: usize, handles: &[Handle]) {
         let mut context_object_changed = false;
         for &handle in handles {
+            // A dimension is drawn from the block holding its picture, and that
+            // picture was made under the settings just edited. Drop it so the
+            // dimension is drawn afresh — otherwise the edit changes the stored
+            // variables and nothing on screen.
+            if matches!(
+                self.tabs[i].scene.document.get_entity(handle),
+                Some(acadrust::EntityType::Dimension(_))
+            ) {
+                self.tabs[i].scene.invalidate_dim_block_recorded(handle);
+            }
             context_object_changed |= self.tabs[i]
                 .scene
                 .sync_displayed_annotation_context(handle);