Point clouds: PCEXTRACTEDGE, PCEXTRACTCORNER, PCEXTRACTCENTERLINE, PCEXTRACTSECTION

Planes are found from the cloud points under the pick and grown over
the connected points on them: two planes give a line along their
intersection over the points' extent, three a point at their corner.
A cylindrical segment gives a line along its axis. A live section
object traces the points on its kept side as polylines or lines in the
section plane, with a preview and Accept/Settings/Undo;
-PCEXTRACTSECTION creates them directly.

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>

src/app/commands/mod.rs

@@ -15,6 +15,7 @@ mod layerprops;
 mod layers;
 pub(crate) mod pdf_import;
 mod point_cloud;
+mod pc_extract;
 mod pdf_underlay;
 mod pdf_dialogs;
 mod xclip;
@@ -270,6 +271,9 @@ impl OpenCADStudio {
         if let Some(t) = self.dispatch_pdf_underlay(cmd, i) {
             return Some(t);
         }
+        if let Some(t) = self.dispatch_pc_extract(cmd, i) {
+            return Some(t);
+        }
         if let Some(t) = self.dispatch_draw(cmd, i) {
             return Some(t);
         }