chore(core): keep the comment share of the first-pass hide files at or under their base

The comment ratchet counts one added comment line each in entry.ts, init.ts and capture.ts, and a
new file above its package's share. The three lines are gone, and the one note that has to stay
(why the hide runs at script evaluation) now lives in the new module's shorter header.

Author: miguel-heygen

packages/core/src/runtime/entry.ts

@@ -29,7 +29,6 @@ type HyperframeWindow = Window & {
 // at script evaluation time, while the document is still parsing.
 installAuthoredOpacityCapture();
 
-// Also at evaluation time: the body is parsed, and may paint, before init runs at DOMContentLoaded.
 hideTimedClipsUntilFirstPass();
 
 // Expose runtime helpers immediately so composition scripts can use them

packages/core/src/runtime/init.ts

@@ -2532,7 +2532,6 @@ export function initSandboxRuntimeModular(): void {
         timedClipDisplayNoneApplied.add(rawNode);
       }
     }
-    // Grading registers only media it can see, and media inside a clip was hidden until now.
     if (decidedTimedClip && revealTimedClipsAfterFirstPass()) colorGradingRuntime?.refresh();
     // Only when a `data-hidden` mutation actually moved something: the skips
     // this reschedule exists to re-run are what change the active set, so

packages/core/src/runtime/timedClipHide.ts

@@ -1,6 +1,6 @@
-// Until the first visibility pass decides each timed clip, a paused page would paint every clip at once
-// (and decode every scene's images). Media is left out: init's media pass owns it.
-// The rule and its flag live on the page, not in this module: every runtime copy on the page shares them.
+// Hides timed non-media clips from script evaluation until the first visibility pass decides them;
+// before it, a paused page painted every clip at once. Media is left to init's media pass.
+// The rule and its flag live on the page, so every runtime copy shares them.
 const HIDE_ATTR = "data-hf-first-pass-hide";
 const HIDE_UNTIL_FIRST_PASS =
   "[data-start]:not(video, audio, img) { visibility: hidden !important; }";
@@ -24,7 +24,7 @@ export function hideTimedClipsUntilFirstPass(): void {
   win.__hfFirstPassHidden = true;
 }
 
-/** True when this call lifted the rule. */
+/** True when this call lifted the rule; callers then re-register what skipped hidden elements (grading). */
 export function revealTimedClipsAfterFirstPass(): boolean {
   const win = window as FirstPassWindow;
   if (!win.__hfFirstPassHidden) return false;

packages/shader-transitions/src/capture.ts

@@ -55,7 +55,6 @@ export function forceSceneVisibleInClone(source: HTMLElement, cloneDoc: Document
   if (!(clone instanceof HTMLElement)) return;
 
   clone.style.opacity = "1";
-  // Important: the runtime hides timed clips with an !important rule until its first visibility pass.
   clone.style.setProperty("visibility", "visible", "important");
   clone.querySelectorAll<HTMLElement>("[data-start]").forEach((el) => {
     el.style.setProperty("visibility", "visible", "important");