Merge the startup, clipboard, animation-preview and UI PRs integrated on land-r5 (#644 #652 #655 #702 #571 #539 #674 #648 #697 #479 #369 #368)

# Conflicts:
#	crates/ui-egui/src/canvas.rs
#	crates/ui-egui/src/ribbon.rs

crates/engine/src/tools.rs

@@ -369,7 +369,7 @@ impl Session {
         }
     }
 
-    fn begin(&mut self, label: &str) {
+    pub(crate) fn begin(&mut self, label: &str) {
         if let Some(st) = self.active_mut()
             && st.interaction.is_none()
         {
@@ -386,6 +386,14 @@ impl Session {
         }
     }
 
+    /// End the interaction only when it is the one `label` started. A twist must not commit a drag.
+    pub(crate) fn commit_named(&mut self, label: &str) {
+        let ours = self.active().and_then(|st| st.interaction.as_ref()).is_some_and(|i| i.label == label);
+        if ours {
+            self.commit();
+        }
+    }
+
     fn down(&mut self, p: Point, mods: Mods, tol: f64) -> Result<Value> {
         if let Some(Drag::Freeform { mode, mut points, .. }) = self.tool.drag.clone() {
             // Next click of a freeform: close on the start point, else add a vertex.