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, 39 insertions, 0 deletions

diff --git a/apps/web/src/lib/animation/index.ts b/apps/web/src/lib/animation/index.ts
new file mode 100644
index 00000000..c41c1a7e
--- /dev/null
+++ b/apps/web/src/lib/animation/index.ts
@@ -0,0 +1,39 @@
+export {
+	getChannelValueAtTime,
+	getNumberChannelValueAtTime,
+	normalizeChannel,
+} from "./interpolation";
+
+export {
+	clampAnimationsToDuration,
+	cloneAnimations,
+	getChannel,
+	removeElementKeyframe,
+	retimeElementKeyframe,
+	setChannel,
+	splitAnimationsAtTime,
+	upsertElementKeyframe,
+} from "./keyframes";
+
+export {
+	getElementLocalTime,
+	resolveOpacityAtTime,
+	resolveTransformAtTime,
+	resolveVolumeAtTime,
+} from "./resolve";
+
+export {
+	coerceAnimationValueForProperty,
+	getAnimationPropertyDefinition,
+	getDefaultInterpolationForProperty,
+	getElementBaseValueForProperty,
+	isAnimationPropertyPath,
+	supportsAnimationProperty,
+	withElementBaseValueForProperty,
+} from "./property-registry";
+
+export {
+	getElementKeyframes,
+	getKeyframeAtTime,
+	hasKeyframesForPath,
+} from "./keyframe-query";