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, 3 insertions, 3 deletions

diff --git a/apps/web/src/lib/timeline/element-utils.ts b/apps/web/src/lib/timeline/element-utils.ts
index c51667bf..9e191833 100644
--- a/apps/web/src/lib/timeline/element-utils.ts
+++ b/apps/web/src/lib/timeline/element-utils.ts
@@ -18,7 +18,7 @@ import type {
 	AudioElement,
 	VideoElement,
 	ImageElement,
-	StickerElement,
+	VisualElement,
 	UploadAudioElement,
 } from "@/types/timeline";
 import type { MediaType } from "@/types/assets";
@@ -31,7 +31,7 @@ export function canElementHaveAudio(
 
 export function isVisualElement(
 	element: TimelineElement,
-): element is VideoElement | ImageElement | TextElement | StickerElement {
+): element is VisualElement {
 	return (
 		element.type === "video" ||
 		element.type === "image" ||
@@ -42,7 +42,7 @@ export function isVisualElement(
 
 export function canElementBeHidden(
 	element: TimelineElement,
-): element is VideoElement | ImageElement | TextElement | StickerElement {
+): element is VisualElement {
 	return element.type !== "audio";
 }