Never crash: project crate without expect()

Layer::motion_trackers_mut expect()ed the group it had just inserted; it returns an Option
now and track.motion reports an error if the group is somehow missing. Denies the panic
lints in the crate (the project model behind .ecproj files).

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

clippy.toml

@@ -0,0 +1,4 @@
+allow-unwrap-in-tests = true
+allow-expect-in-tests = true
+allow-panic-in-tests = true
+allow-indexing-slicing-in-tests = true

crates/engine/src/commands/track.rs

@@ -214,7 +214,7 @@ fn create(s: &mut Session, p: &V, cmd: &str) -> Result<V> {
         let mut ids = Ids(&mut next);
         let g = tracking::tracker(&mut ids, &name, st, &pts);
         let uid = g.uid;
-        l.motion_trackers_mut(&mut ids).children.push(g.into());
+        l.motion_trackers_mut(&mut ids).ok_or_else(|| bad(cmd, "the layer has no Motion Trackers group"))?.children.push(g.into());
         proj.next_id = next;
         state.current_track = Some((lid, uid));
         state.selected_layers = vec![lid];

crates/project/src/lib.rs

@@ -4,6 +4,8 @@
 //! ([`props`]). Compositions sit behind `Arc` so undo snapshots share everything that did not
 //! change.
 
+#![deny(clippy::unwrap_used, clippy::expect_used, clippy::panic, clippy::unimplemented, clippy::todo, clippy::unreachable)]
+
 pub mod build;
 pub mod essential;
 pub mod props;

crates/project/src/tracking.rs

@@ -235,11 +235,11 @@ impl Layer {
         self.trackers().find(|(g, _)| g.uid == uid)
     }
     /// The Motion Trackers group, created (first in the layer's tree, like AE) when missing.
-    pub fn motion_trackers_mut(&mut self, ids: &mut Ids) -> &mut PropGroup {
+    pub fn motion_trackers_mut(&mut self, ids: &mut Ids) -> Option<&mut PropGroup> {
         if self.props.sub(MOTION_TRACKERS).is_none() {
             self.props.children.insert(0, motion_trackers(ids).into());
         }
-        self.props.sub_mut(MOTION_TRACKERS).expect("motion trackers group")
+        self.props.sub_mut(MOTION_TRACKERS)
     }
 }