View state: hide, show and isolate viewport items, saved with the model

view.hide, view.show, view.isolate and view.show_all change which
bodies, surfaces, datums, boundary conditions, loads, reference points
and couplings the viewport draws. The hidden items are view state: the
manifest's `view` keeps them, a change marks the model unsaved, but it
is neither journalled nor undone and leaves results current. Items that
go away are forgotten. Headless pictures leave hidden items out; the
glyph builders take a filter. Tools > View > Show All claims the
commands.

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01UhhZMBTviDQxZvwnyP89fo

crates/ui-egui/src/scene.rs

@@ -84,7 +84,7 @@ pub fn symbols(
 
 /// Draw the model's datum planes and axes around `bounds` into `s`; returns the box around them.
 pub fn datums(s: &mut Scene, model: &fieldcraft_model::Model, bounds: &Aabb3, t: &Tokens) -> Aabb3 {
-    fieldcraft_render::glyphs::datums(model, bounds, &t.glyph_colors(), s)
+    fieldcraft_render::glyphs::datums(model, bounds, &|_| true, &t.glyph_colors(), s)
 }
 
 /// The scene for `display` drawn in `style`.