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, 30 insertions, 10 deletions

diff --git a/apps/web/src/lib/commands/timeline/element/update-element-duration.ts b/apps/web/src/lib/commands/timeline/element/update-element-duration.ts
index 6b3a860b..3366548d 100644
--- a/apps/web/src/lib/commands/timeline/element/update-element-duration.ts
+++ b/apps/web/src/lib/commands/timeline/element/update-element-duration.ts
@@ -1,28 +1,48 @@
 import { Command } from "@/lib/commands/base-command";
 import type { TimelineTrack } from "@/types/timeline";
 import { EditorCore } from "@/core";
+import { clampAnimationsToDuration } from "@/lib/animation";
 
 export class UpdateElementDurationCommand extends Command {
 	private savedState: TimelineTrack[] | null = null;
+	private readonly trackId: string;
+	private readonly elementId: string;
+	private readonly duration: number;
 
-	constructor(
-		private trackId: string,
-		private elementId: string,
-		private duration: number,
-	) {
+	constructor({
+		trackId,
+		elementId,
+		duration,
+	}: {
+		trackId: string;
+		elementId: string;
+		duration: number;
+	}) {
 		super();
+		this.trackId = trackId;
+		this.elementId = elementId;
+		this.duration = duration;
 	}
 
 	execute(): void {
 		const editor = EditorCore.getInstance();
 		this.savedState = editor.timeline.getTracks();
 
-		const updatedTracks = this.savedState.map((t) => {
-			if (t.id !== this.trackId) return t;
-			const newElements = t.elements.map((el) =>
-				el.id === this.elementId ? { ...el, duration: this.duration } : el,
+		const updatedTracks = this.savedState.map((track) => {
+			if (track.id !== this.trackId) return track;
+			const newElements = track.elements.map((element) =>
+				element.id === this.elementId
+					? {
+							...element,
+							duration: this.duration,
+							animations: clampAnimationsToDuration({
+								animations: element.animations,
+								duration: this.duration,
+							}),
+						}
+					: element,
 			);
-			return { ...t, elements: newElements } as typeof t;
+			return { ...track, elements: newElements } as typeof track;
 		});
 
 		editor.timeline.updateTracks(updatedTracks);