fix(studio): address timeline PR review — drop dead code, add fadeIn keyframes, compSrc test

packages/studio/src/player/components/CompositionThumbnail.tsx

@@ -5,7 +5,6 @@ interface CompositionThumbnailProps {
   previewUrl: string;
   label: string;
   labelColor: string;
-  accentColor?: string;
   selector?: string;
   selectorIndex?: number;
   seekTime?: number;
@@ -52,7 +51,6 @@ export const CompositionThumbnail = memo(function CompositionThumbnail({
   previewUrl,
   label,
   labelColor,
-  accentColor: _accentColor = "#6B7280",
   selector,
   selectorIndex,
   seekTime = 2,
@@ -112,7 +110,7 @@ export const CompositionThumbnail = memo(function CompositionThumbnail({
       {loaded && (
         <div
           className="absolute inset-0 flex"
-          style={{ animation: "fadeIn 200ms ease-out", mixBlendMode: "lighten" }}
+          style={{ animation: "hf-thumb-fade 200ms ease-out", mixBlendMode: "lighten" }}
         >
           {Array.from({ length: frameCount }).map((_, i) => (
             <div

packages/studio/src/player/components/timelineTheme.ts

@@ -35,17 +35,13 @@ export interface TimelineTheme {
   clipRadius: string;
 }
 
-const UNIFIED_STYLE: TimelineTrackStyle = {
+const TRACK_STYLE: TimelineTrackStyle = {
   clip: "#1c2028",
   accent: "#3CE6AC",
   label: "#dde1e8",
   iconBackground: "rgba(255,255,255,0.06)",
 };
 
-function createTrackStyle(_tag: string): TimelineTrackStyle {
-  return UNIFIED_STYLE;
-}
-
 export const defaultTimelineTheme: TimelineTheme = {
   shellBackground: "#0A0A0B",
   shellBorder: "rgba(255,255,255,0.05)",
@@ -74,16 +70,8 @@ export const defaultTimelineTheme: TimelineTheme = {
   clipRadius: "6px",
 };
 
-export function getTimelineTrackStyle(tag: string): TimelineTrackStyle {
-  const normalized = tag.toLowerCase();
-  if (
-    normalized.startsWith("h") &&
-    normalized.length === 2 &&
-    "123456".includes(normalized[1] ?? "")
-  ) {
-    return createTrackStyle("h1");
-  }
-  return createTrackStyle(normalized);
+export function getTimelineTrackStyle(_tag: string): TimelineTrackStyle {
+  return TRACK_STYLE;
 }
 
 export function getClipHandleOpacity({