feat(commands): expand standard CAD command coverage

Integrate a large batch of standard CAD commands and fix several
name/behaviour mismatches, with no product references in code.

3D solids (reusing the truck B-rep pipeline):
- SLICE, INTERFERE, PRESSPULL, POLYSOLID, PYRAMID, SECTION
- 3DROTATE, 3DMIRROR, 3DALIGN (cached-solid transforms)

Annotation / text:
- ARCTEXT, SPLINEFIT (Catmull-Rom to Bezier), DIMJOGGED, OBJECTSCALE
  (XData markers honoured by the existing geometry-gen / tessellator)

Blocks / misc:
- NCOPY (block-content extraction via explode_entity)
- OPTIONS, SYNCPVIEWPORTS, THICKEN, plus earlier toggles, aliases,
  system variables, and layer/style/view commands

POINTCLOUD/RECAP and UNDERLAYLAYERS/UOSNAP are intentionally left out:
they require a proprietary binary / PDF-layer parser, a GPU point
renderer, and real test files.

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

src/modules/draw/clipboard/copy_base.rs

@@ -0,0 +1,39 @@
+// COPYBASE — copy the current selection to the clipboard using a base point the
+// user picks (rather than the selection's centroid, as COPYCLIP does). The
+// command only collects the base point; the host performs the copy when it
+// receives the dispatched `COPYBASE_AT <x> <y> <z>` token.
+
+use glam::DVec3;
+
+use crate::command::{CadCommand, CmdResult};
+
+pub struct CopyBaseCommand;
+
+impl CopyBaseCommand {
+    pub fn new() -> Self {
+        Self
+    }
+}
+
+impl CadCommand for CopyBaseCommand {
+    fn name(&self) -> &'static str {
+        "COPYBASE"
+    }
+
+    fn prompt(&self) -> String {
+        "COPYBASE  Specify base point:".to_string()
+    }
+
+    fn on_point(&mut self, pt: DVec3) -> CmdResult {
+        CmdResult::Dispatch(format!("COPYBASE_AT {} {} {}", pt.x, pt.y, pt.z))
+    }
+
+    fn on_enter(&mut self) -> CmdResult {
+        CmdResult::Cancel
+    }
+}
+
+// ── Autocomplete registry ─────────────────────────────────
+inventory::submit!(crate::command::CommandRegistration {
+    names: &["COPYBASE"]
+}); // CopyBaseCommand

src/modules/draw/clipboard/mod.rs

@@ -1,3 +1,4 @@
+pub mod copy_base;
 pub mod copy_clip;
 pub mod cut;
 pub mod paste;