feat(model): 3D solid modelling tab — primitives + boolean ops

Rename the Home tab to "Draw" and add a Model tab beside it with two
groups:

- Model: BOX / CYLINDER / CONE / SPHERE / WEDGE / TORUS, placed with a
  footprint + height. Each is built as a real ACIS Solid3D (acadrust
  primitive builders) plus a truck B-rep, tessellated into the shaded
  mesh pipeline, with edge wires for picking + wireframe.
- Design: UNION / SUBTRACT / INTERSECT via truck-shapeops.

A session-only Scene.model_solids cache holds each solid's truck B-rep
so the boolean tools can combine and chain them. Supersedes the old
command-line BOX/SPHERE/CYLINDER (insert::solid3d_cmds keeps EXTRUDE/
REVOLVE/SWEEP/LOFT).

Known limitations: booleans need solids created this session; curved
ACIS primitives render in-session but not after reload (the SAT
tessellator handles only planar caps); geometry assumes world_offset 0.

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

src/app/cmd_result.rs

@@ -125,6 +125,16 @@ impl OpenCADStudio {
                 self.tabs[i].snap_result = None;
                 self.restore_pre_cmd_tangent();
             }
+            CmdResult::CommitSolid { entity, solid } => {
+                let label = self.history_label_from_active_cmd(i, "SOLID");
+                self.push_undo_snapshot(i, label);
+                self.add_model_solid(entity, *solid);
+                self.tabs[i].dirty = true;
+                self.tabs[i].scene.clear_preview_wire();
+                self.tabs[i].active_cmd = None;
+                self.tabs[i].snap_result = None;
+                self.restore_pre_cmd_tangent();
+            }
             CmdResult::CommitAndEditText(entity) => {
                 let label = self.history_label_from_active_cmd(i, "ENTITY");
                 self.push_undo_snapshot(i, label);

src/app/commands.rs

@@ -1190,6 +1190,22 @@ impl OpenCADStudio {
                 }
             }
 
+            // ── Model commands (3D primitives) ─────────────────────────────
+            "BOX" | "WEDGE" | "CYLINDER" | "CONE" | "SPHERE" | "TORUS" => {
+                use crate::modules::model::primitive_cmd::PrimitiveCommand;
+                let new_cmd = PrimitiveCommand::new(cmd);
+                self.command_line.push_info(&new_cmd.prompt());
+                self.tabs[i].active_cmd = Some(Box::new(new_cmd));
+            }
+
+            // ── Design commands (solid booleans) ───────────────────────────
+            "UNION" | "SUBTRACT" | "INTERSECT" => {
+                use crate::modules::model::boolean_cmd::BoolOp;
+                if let Some(op) = BoolOp::from_id(cmd) {
+                    return self.solid_boolean(op);
+                }
+            }
+
             // ── Annotate commands ──────────────────────────────────────────
             "TEXT" | "T" | "DT" => {
                 use crate::modules::annotate::text::TextCommand;
@@ -5038,32 +5054,8 @@ impl OpenCADStudio {
                 }
             }
 
-            // ── 3D Primitive — BOX ────────────────────────────────────────
-            "BOX" => {
-                use crate::modules::insert::solid3d_cmds::BoxCommand;
-                let color = self.tabs[i].scene.layer_color(&self.tabs[i].active_layer);
-                let cmd = BoxCommand::new(color);
-                self.command_line.push_info(&cmd.prompt());
-                self.tabs[i].active_cmd = Some(Box::new(cmd));
-            }
-
-            // ── 3D Primitive — SPHERE ─────────────────────────────────────
-            "SPHERE" => {
-                use crate::modules::insert::solid3d_cmds::SphereCommand;
-                let color = self.tabs[i].scene.layer_color(&self.tabs[i].active_layer);
-                let cmd = SphereCommand::new(color);
-                self.command_line.push_info(&cmd.prompt());
-                self.tabs[i].active_cmd = Some(Box::new(cmd));
-            }
-
-            // ── 3D Primitive — CYLINDER ───────────────────────────────────
-            "CYLINDER" => {
-                use crate::modules::insert::solid3d_cmds::CylinderCommand;
-                let color = self.tabs[i].scene.layer_color(&self.tabs[i].active_layer);
-                let cmd = CylinderCommand::new(color);
-                self.command_line.push_info(&cmd.prompt());
-                self.tabs[i].active_cmd = Some(Box::new(cmd));
-            }
+            // BOX / SPHERE / CYLINDER / CONE / WEDGE / TORUS are handled by the
+            // Model-tab primitive command above (with truck boolean caching).
 
             // ── EXTRUDE ────────────────────────────────────────────────────
             "EXTRUDE" | "EXT" => {

src/app/mod.rs

@@ -5,6 +5,7 @@ mod helpers;
 mod history;
 mod layers;
 mod mtext_editor;
+mod model_ops;
 mod properties;
 mod text_inline;
 mod update;

src/app/model_ops.rs

@@ -0,0 +1,75 @@
+// 3D solid modelling support on the App: committing Model-tab primitives,
+// and the Design-group boolean operations (truck-shapeops) over the scene's
+// session-cached truck B-reps.
+
+use acadrust::entities::Solid3D;
+use acadrust::{EntityType, Handle};
+use iced::Task;
+use truck_modeling::Solid;
+
+use super::Message;
+use crate::modules::model::boolean_cmd::BoolOp;
+use crate::scene::model_solid::{self, Bool};
+
+impl super::OpenCADStudio {
+    /// Commit a Model-tab solid: add its acadrust entity to the document, then
+    /// register the truck B-rep (caches it for booleans + tessellates it into
+    /// the shaded mesh pipeline). Returns the new entity handle.
+    pub(super) fn add_model_solid(&mut self, entity: EntityType, solid: Solid) -> Handle {
+        let i = self.active_tab;
+        let Some(handle) = self.commit_entity_handle(entity) else {
+            return Handle::NULL;
+        };
+        self.tabs[i].scene.register_model_solid(handle, solid);
+        handle
+    }
+
+    /// Run a boolean (`union` / `subtract` / `intersect`) on exactly two
+    /// selected solids whose truck B-reps are in the session cache.
+    pub(super) fn solid_boolean(&mut self, op: BoolOp) -> Task<Message> {
+        let i = self.active_tab;
+        // Selected entities that have a cached truck B-rep.
+        let handles: Vec<Handle> = self.tabs[i]
+            .scene
+            .selected
+            .iter()
+            .copied()
+            .filter(|h| self.tabs[i].scene.model_solids.contains_key(h))
+            .collect();
+        if handles.len() != 2 {
+            self.command_line.push_error(
+                "Boolean: select exactly two solids created this session.",
+            );
+            return Task::none();
+        }
+        let a = self.tabs[i].scene.model_solids[&handles[0]].clone();
+        let b = self.tabs[i].scene.model_solids[&handles[1]].clone();
+        let kind = match op {
+            BoolOp::Union => Bool::Union,
+            BoolOp::Subtract => Bool::Subtract,
+            BoolOp::Intersect => Bool::Intersect,
+        };
+        let Some(result) = model_solid::boolean(kind, &a, &b) else {
+            self.command_line
+                .push_error("Boolean failed — the solids may not overlap.");
+            return Task::none();
+        };
+
+        self.push_undo_snapshot(i, "BOOLEAN");
+        // Remove the two operands (entity + mesh + cached B-rep).
+        self.tabs[i].scene.erase_entities(&handles);
+        // The result is freshly combined geometry with no ACIS parametrisation,
+        // so it lives as a Solid3D whose render/boolean data is the injected
+        // truck mesh + cached B-rep; its edge wires make it pickable.
+        let mut s3d = Solid3D::new();
+        s3d.wires = model_solid::edge_wires(&result);
+        let handle = self.add_model_solid(EntityType::Solid3D(s3d), result);
+        self.tabs[i].scene.deselect_all();
+        if !handle.is_null() {
+            self.tabs[i].scene.select_entity(handle, false);
+        }
+        self.tabs[i].dirty = true;
+        self.refresh_properties();
+        Task::none()
+    }
+}