fix: make vhsTracking accept ChoreoContext directly, remove as any cast

Effect functions now accept FightContext | ChoreoContext union type,
eliminating the unsafe cast in rounds.ts.

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

frontend/src/game/fight/effects.ts

@@ -1,7 +1,9 @@
 import type { GameObj } from 'kaplay'
-import type { FightContext } from './types'
+import type { FightContext, ChoreoContext } from './types'
 
-export function glitchRGB(ctx: FightContext, duration: number = 0.2): void {
+type EffectContext = FightContext | ChoreoContext
+
+export function glitchRGB(ctx: EffectContext, duration: number = 0.2): void {
   const { k, W, H, safeColor, trackedTimeout } = ctx
   const layers = [
     { color: '#ff0000', dx: 4 + Math.random() * 6, dy: -2 },
@@ -20,7 +22,7 @@ export function glitchRGB(ctx: FightContext, duration: number = 0.2): void {
   }
 }
 
-export function scanlineGlitch(ctx: FightContext, duration: number = 0.3): void {
+export function scanlineGlitch(ctx: EffectContext, duration: number = 0.3): void {
   const { k, W, H, safeColor } = ctx
   const lines: GameObj[] = []
   const count = 6 + Math.floor(Math.random() * 8)
@@ -41,7 +43,7 @@ export function scanlineGlitch(ctx: FightContext, duration: number = 0.3): void
   ctx.trackedTimeout(() => { lines.forEach(l => { if (l.exists()) l.destroy() }) }, duration * 1000)
 }
 
-export function vhsTracking(ctx: FightContext, duration: number = 0.4): void {
+export function vhsTracking(ctx: EffectContext, duration: number = 0.4): void {
   const { k, W, H, safeColor, theme } = ctx
   const bands: GameObj[] = []
   const bandCount = 3
@@ -61,7 +63,7 @@ export function vhsTracking(ctx: FightContext, duration: number = 0.4): void {
   ctx.trackedTimeout(() => { bands.forEach(b => { if (b.exists()) b.destroy() }) }, duration * 1000)
 }
 
-export function dimensionalShift(ctx: FightContext, duration: number = 0.6): void {
+export function dimensionalShift(ctx: EffectContext, duration: number = 0.6): void {
   const { k, W, H, safeColor, trackedInterval, trackedTimeout, clearTracked } = ctx
   const colors = ['#ff00ff', '#00ffff', '#ff0000', '#0000ff', '#ffff00']
   let idx = 0

frontend/src/game/fight/rounds.ts

@@ -64,9 +64,8 @@ export function createRoundSystem(ctx: ChoreoContext, deps: RoundDeps) {
     showSpeechBubble,
   } = deps
 
-  // Local vhsTracking wrapper — effects.ts expects FightContext, pass ctx as compatible
   function vhsTracking(duration?: number) {
-    _vhsTracking(ctx as any, duration)
+    _vhsTracking(ctx, duration)
   }
 
   const heartfeltLines = [