feat(array): ARRAYRECT and ARRAYPOLAR create associative arrays

With the new Associative option on (the default), ARRAYRECT and
ARRAYPOLAR build the array the way the drawing format stores one: the
selected objects move into an anonymous source block, an anonymous
array block holds one ByBlock reference to it per item, an INSERT of
the array block takes their place, and an AcDbAssocAction with an
AcDbAssocArrayActionBody, its three dependencies, the BaseNormal /
Origin / basePoint parameters and the value parameters tie them
together in the model-space network. The array is then edited from
Properties like an array read from a file.

The option flips with AS and is remembered for the session; on a
rotated working plane the commands keep making plain copies. Saving
drops the action of an array whose reference was erased or exploded.

Checked: created arrays reopen as associative with their parameters
and items, and the ODA converter reads the saved DWG without errors.

Refs #1109

Co-Authored-By: Claude Opus 5.5 <[email protected]>

src/command.rs

@@ -1621,6 +1621,11 @@ pub enum CmdResult {
     },
     /// Copy selected entities with multiple transforms (e.g. rectangular array); end command.
     BatchCopy(Vec<Handle>, Vec<EntityTransform>),
+    /// Turn the objects into an associative array; end command.
+    AssocArray {
+        handles: Vec<Handle>,
+        spec: crate::scene::assoc_array::AssocArraySpec,
+    },
     /// Erase `handle` and replace with new entities; command stays active.
     ReplaceEntity(Handle, Vec<EntityType>),
     /// XCLIP on block references; ends the command.