Insert: Summary, Section and Slide Zoom with Return to Zoom

Insert › Links gains Zoom, with PowerPoint's three kinds: Slide Zoom
(pictures of chosen slides on the current slide), Section Zoom (one per
chosen section) and Summary Zoom (a new Title Only slide in front of
the chosen parts). Each zoom is a picture of its target that jumps to
it in the show. With Return to Zoom, on by default for section and
summary zooms as in PowerPoint, the show comes back to the zoom slide,
fully built, after the target slide or the section's last slide; going
elsewhere (a slide number, See All Slides) forgets it. Hyperlink gains
zoom_return for this; .pptx saves zooms as the linked pictures
PowerPoint writes as their fallback, so the return flag is DeckCraft-
only for now. Live thumbnails, the zoom-in animation and the native
p166:sldZm element are still missing; gaps.md says so.

Co-authored-by: Cursor <cursoragent@cursor.com>

crates/engine/src/cmd/insert.rs

@@ -589,7 +589,7 @@ fn hyperlink(s: &mut Session, p: &Value) -> Result<Value> {
         return Err(bad("insert.hyperlink", "missing `url` or `slide`"));
     };
     let display = str_param(p, "text").map_or(display, str::to_string);
-    let link = Hyperlink { action, tooltip: str_param(p, "tooltip").unwrap_or("").to_string(), highlight_click: false };
+    let link = Hyperlink { action, tooltip: str_param(p, "tooltip").unwrap_or("").to_string(), highlight_click: false, zoom_return: None };
     if s.doc()?.selection.text.is_some() {
         return super::text::link_text(s, link, &display);
     }
@@ -621,7 +621,7 @@ fn action_button(s: &mut Session, p: &Value) -> Result<Value> {
         xfrm: Some(rect),
         geom: Geom::preset(preset),
         style: Some(ShapeStyle::accent(SchemeSlot::Accent1)),
-        click: action.map(|a| Hyperlink { action: a, tooltip: String::new(), highlight_click: true }),
+        click: action.map(|a| Hyperlink { action: a, tooltip: String::new(), highlight_click: true, zoom_return: None }),
         ..Default::default()
     };
     let id = add_shape(s, shape, true)?;