feat(node_graph,effect_stack): programmatic selection and card selection events

NodeGraphView::set_selection selects nodes programmatically (emitting
SelectionChanged); EffectStackDataSource::selected_effect highlights
the chosen card and EffectStackEvent::CardSelected reports card clicks
— the two-way clip/node selection sync between the timeline, node
editor and inspector.

crates/gpui/examples/learn/effect_stack.rs

@@ -198,6 +198,7 @@ impl StackDemoRoot {
 						| EffectStackEvent::RemoveRequested(_)
 						| EffectStackEvent::AddRequested { .. }
 						| EffectStackEvent::ContextMenuRequested { .. }
+						| EffectStackEvent::CardSelected { .. }
 						| EffectStackEvent::ParameterChanged { .. } => {
 							todo!("apply {event:?} to the mock model (or engine, in a real app)")
 						}

crates/gpui/src/effect_stack/data.rs

@@ -162,6 +162,15 @@ pub trait EffectStackDataSource: 'static {
 	/// state instead of cards and suppresses all card interactions.
 	fn target_label(&self) -> Option<SharedString>;
 
+	/// The card the stack should highlight as selected — the effect whose
+	/// node is selected in the node graph, when the two views are linked.
+	/// `None` means no card is highlighted. Defaults to `None`.
+	///
+	/// This is a read-only selection mirror; the view never mutates it.
+	fn selected_effect(&self) -> Option<EffectId> {
+		None
+	}
+
 	/// Whether dropping the given effect at `new_index` (an index into the
 	/// list returned by [`effects`](EffectStackDataSource::effects)) would
 	/// be a valid reorder.

crates/gpui/src/effect_stack/stack_view.rs

@@ -67,6 +67,14 @@ pub enum EffectStackEvent {
 		/// The desired new expansion state.
 		expanded: bool,
 	},
+	/// The user clicked a card header to select it (the same gesture that
+	/// toggles expansion). Emitted alongside
+	/// [`ExpansionToggled`](Self::ExpansionToggled) so hosts can sync the
+	/// effect selection with the node graph (highlighting the effect's node).
+	CardSelected {
+		/// The clicked effect.
+		effect: EffectId,
+	},
 	/// The user clicked the remove button on a removable card.
 	RemoveRequested(EffectId),
 	/// The user invoked an "add effect" affordance at a stack position.
@@ -274,7 +282,9 @@ impl<D: EffectStackDataSource> EffectStackView<D> {
 	}
 
 	/// Toggles a card's expansion by emitting
-	/// [`EffectStackEvent::ExpansionToggled`].
+	/// [`EffectStackEvent::ExpansionToggled`], and reports the card click as
+	/// [`EffectStackEvent::CardSelected`] so hosts can sync the node-graph
+	/// selection with the stack.
 	fn toggle_expanded(&mut self, id: EffectId, cx: &mut Context<Self>) {
 		self.drag_state = DragState::default();
 		let expanded = self
@@ -289,6 +299,7 @@ impl<D: EffectStackDataSource> EffectStackView<D> {
 			effect: id,
 			expanded,
 		});
+		cx.emit(EffectStackEvent::CardSelected { effect: id });
 		cx.notify();
 	}
 
@@ -360,9 +371,9 @@ impl<D: EffectStackDataSource> Render for EffectStackView<D> {
 			self.drag_state = DragState::default();
 		}
 
-		let (label, effects) = {
+		let (label, effects, selected_effect) = {
 			let data = self.data.read(cx);
-			(data.target_label(), data.effects())
+			(data.target_label(), data.effects(), data.selected_effect())
 		};
 		let insertion_index = self.drag_state.insertion_index;
 		let dragged_id = self.drag_state.dragged;
@@ -532,7 +543,9 @@ impl<D: EffectStackDataSource> Render for EffectStackView<D> {
 				.w_full()
 				.rounded_md()
 				.border_1()
-				.border_color(if fixed {
+				.border_color(if selected_effect == Some(id) {
+					colors.selected
+				} else if fixed {
 					colors.border
 				} else {
 					colors.separator

crates/gpui/src/node_graph/graph_view.rs

@@ -318,6 +318,16 @@ impl<D: NodeGraphDataSource + 'static> NodeGraphView<D> {
 		&mut self.state
 	}
 
+	/// Programmatically replaces the selection (e.g. to sync the graph with
+	/// a timeline selection or an inspector card click). Emits
+	/// [`NodeGraphEvent::SelectionChanged`] when the set changed, so hosts
+	/// keep their engine-side selection mirror consistent. Callers should
+	/// not call `cx.notify()` on the view themselves — this method does.
+	pub fn set_selection(&mut self, nodes: BTreeSet<NodeId>, cx: &mut Context<Self>) {
+		self.set_selection_and_emit(nodes, cx);
+		cx.notify();
+	}
+
 	/// Returns the data-source entity this view renders.
 	pub fn data(&self) -> &Entity<D> {
 		&self.data