Merge PR #520 from NikitkaRa: Insert: Summary, Section and Slide Zoom with Return to Zoom

Fix-ups in the merge (review): zoom targets, sections and titles are looked up with get()
instead of indexing; Hyperlink literals carry both main's sound fields and zoom_return;
duplicated test statements left by the test-file union are removed.

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

crates/engine/src/cmd/mod.rs

@@ -26,6 +26,7 @@ pub mod smartart;
 pub mod table;
 pub mod text;
 pub mod transition;
+pub mod zoom;
 
 use deckcraft_geom::Xfrm;
 use deckcraft_model::ShapeId;
@@ -183,6 +184,7 @@ pub fn command_specs() -> &'static [CommandSpec] {
         v.extend(inspect::specs());
         v.extend(media::specs());
         v.extend(artistic::specs());
+        v.extend(zoom::specs());
         v
     })
 }