feat: implement keyframe animation system

Add keyframe support for transform, opacity, and volume properties.
Includes animation engine (interpolation, mutations, resolvers), timeline
markers with selection/snapping, properties panel toggles, keyframe-aware
renderer, and full undo/redo command support.

Also refactor element command constructors to object params, extract
timeline pixel math to pixel-utils.ts, and update cursor rules.

1 files changed, 12 insertions, 2 deletions

diff --git a/apps/web/src/lib/commands/timeline/element/duplicate-elements.ts b/apps/web/src/lib/commands/timeline/element/duplicate-elements.ts
index cf1bd94c..97b475f4 100644
--- a/apps/web/src/lib/commands/timeline/element/duplicate-elements.ts
+++ b/apps/web/src/lib/commands/timeline/element/duplicate-elements.ts
@@ -6,6 +6,7 @@ import {
 	buildEmptyTrack,
 	getHighestInsertIndexForTrack,
 } from "@/lib/timeline/track-utils";
+import { cloneAnimations } from "@/lib/animation";
 
 interface DuplicateElementsParams {
 	elements: { trackId: string; elementId: string }[];
@@ -32,7 +33,7 @@ export class DuplicateElementsCommand extends Command {
 
 		for (const track of this.savedState) {
 			const elementsToDuplicate = this.elements.filter(
-				(el) => el.trackId === track.id,
+				(elementEntry) => elementEntry.trackId === track.id,
 			);
 
 			if (elementsToDuplicate.length === 0) {
@@ -114,5 +115,14 @@ function buildDuplicateElement({
 	id: string;
 	startTime: number;
 }): TimelineElement {
-	return { ...element, id, name: `${element.name} (copy)`, startTime };
+	return {
+		...element,
+		id,
+		name: `${element.name} (copy)`,
+		startTime,
+		animations: cloneAnimations({
+			animations: element.animations,
+			shouldRegenerateKeyframeIds: true,
+		}),
+	};
 }