feat(display): add model lineweight scale

src/scene/mod.rs

@@ -1469,6 +1469,8 @@ pub struct Scene {
     /// Whether entity transparency is honoured on screen. When false the
     /// wire shader forces every line opaque (a uniform toggle, no retessellate).
     pub transparency_display: bool,
+    /// User-adjustable model-space lineweight preview multiplier.
+    pub model_lineweight_scale: f32,
     /// Selection filter: entity-type names excluded from interactive picking.
     /// Empty = every type is selectable.
     pub selection_filter: HashSet<String>,
@@ -1878,6 +1880,7 @@ impl Scene {
             refedit_keep: None,
             hover_highlight: None,
             transparency_display: true,
+            model_lineweight_scale: 1.0,
             selection_filter: HashSet::default(),
             preview_wires: vec![],
             preview_hatches: Arc::new(Vec::new()),

src/scene/pipeline/uniforms.rs

@@ -25,8 +25,8 @@ pub struct Uniforms {
     /// zooming inside MSPACE changes one scalar instead of re-tessellating and
     /// re-uploading every dashed wire.
     pub linetype_scale: f32,
-    /// Multiplier for screen-space lineweights. Model space keeps `1.0`;
-    /// paper layouts derive it from the current paper zoom.
+    /// Multiplier for screen-space lineweights. Model space uses the user's
+    /// preview scale; paper layouts derive it from the current paper zoom.
     pub lineweight_scale: f32,
 
     // ── Relative-to-eye (double-single) additions ───────────────────────────

src/scene/view/render.rs

@@ -3847,7 +3847,9 @@ impl Scene {
             full_bounds,
             self.document.header.lineweight_display || display_plot_lineweights,
         );
-        if self.current_layout != "Model" {
+        if self.current_layout == "Model" {
+            uniforms.lineweight_scale = self.model_lineweight_scale;
+        } else {
             let paper_per_pixel = 2.0 * self.camera.borrow().ortho_size() / canvas.1.max(1.0);
             let paper_units_per_mm = self.paper_space_unit_factor() as f32;
             uniforms.lineweight_scale = paper_units_per_mm / paper_per_pixel / MM_TO_PX;