fix(captions): address code review round 3 findings

- Fix blank snapshot at frame 120 (4.0s is past linger window); use
  frame 85 (2.83s) which lands mid-word showing spoken+active states
- Document KaraokeSweep's intentionally unused spring config in registry

Author: Talha Jubair Siam

src/remotion/captions/visual-snapshot.ts

@@ -25,8 +25,10 @@ const STYLES = [
   "box_highlight",
 ] as const;
 
-// Test frames: word 1 unspoken (frame 0), word 3 active (frame 60), word 5 spoken (frame 120)
-const TEST_FRAMES = [0, 60, 120] as const;
+// Test frames: all unspoken (frame 0), mid-chunk active (frame 60), final word active (frame 85 = 2.83s)
+// Frame 85 lands during "percent" (2.5-3.0s) so we see a mix of spoken + active states.
+// (Frame 120 = 4.0s is past linger window and renders blank.)
+const TEST_FRAMES = [0, 60, 85] as const;
 
 const TEST_WORDS = [
   { word: "The", start: 0.5, end: 0.8 },

src/remotion/compositions/OpenReelsVideo.tsx

@@ -34,6 +34,8 @@ const CAPTION_STYLES: Record<string, { component: React.FC<CaptionStyleProps>; s
   bold_outline:    { component: BoldOutline,    springConfig: { damping: 15, stiffness: 250, mass: 0.5 } },
   clean:           { component: Clean,          springConfig: { damping: 12, stiffness: 200, mass: 0.5 } },
   gradient_rise:   { component: GradientRise,   springConfig: { damping: 8,  stiffness: 150, mass: 0.5 } },
+  // KaraokeSweep uses linear interpolation for its gradient wipe (not spring),
+  // so this springConfig is unused by the style. Kept for registry type uniformity.
   karaoke_sweep:   { component: KaraokeSweep,   springConfig: { damping: 14, stiffness: 220, mass: 0.5 } },
   color_highlight: { component: ColorHighlight, springConfig: { damping: 12, stiffness: 200, mass: 0.5 } },
   block_impact:    { component: BlockImpact,    springConfig: { damping: 18, stiffness: 300, mass: 0.5 } },