Fix: disable snap during entity-pick and selection-gathering modes

Snap is now suppressed (both cursor indicator and coordinate snapping)
when a command is in entity-pick mode (needs_entity_pick) or
selection-gathering mode (is_selection_gathering), and restored
automatically when the mode ends.

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

Cargo.lock

@@ -4,7 +4,7 @@ version = 4
 
 [[package]]
 name = "H7CAD"
-version = "0.1.1"
+version = "0.1.2"
 dependencies = [
  "acadrust",
  "bytemuck",