Add bounding-box object alignment (ALIGNLEFT/TOP/etc.), ported from Mac2CAM

Six one-shot alignment commands for the current selection —
ALIGNLEFT/ALIGNHCENTER/ALIGNRIGHT/ALIGNTOP/ALIGNVCENTER/ALIGNBOTTOM —
distinct from the existing point-picking ALIGN/ALIGN3D command: each
nudges every selected object (or complete group, via new
Scene::selected_object_units) so its bounding-box edge/center lines up
with the extreme edge/center already present in the selection, closer
to a word processor's "align objects" than AutoCAD's 3-point ALIGN.

Wired as plain one-click Tool entries in the Modify extension panel,
next to the existing ALIGN entry, matching that panel's flat-list
convention (no point prompts, so no dropdown submenu needed).

Co-Authored-By: Claude Sonnet 5 <[email protected]>

src/modules/draw/modify/align.rs

@@ -304,6 +304,14 @@ impl AlignCommand {
 }
 
 inventory::submit!(crate::command::CommandRegistration { names: &["ALIGN"] });  // AlignCommand
+// ALIGNLEFT/ALIGNHCENTER/ALIGNRIGHT/ALIGNTOP/ALIGNVCENTER/ALIGNBOTTOM: one-shot
+// bounding-box alignment, dispatched directly (no CadCommand of their own) by
+// `OpenCADStudio::align_selected_bounds` in `src/app/commands/inquiry.rs`.
+inventory::submit!(crate::command::CommandRegistration {
+    names: &[
+        "ALIGNLEFT", "ALIGNHCENTER", "ALIGNRIGHT", "ALIGNTOP", "ALIGNVCENTER", "ALIGNBOTTOM",
+    ],
+});
 
 #[cfg(test)]
 mod tests {