Zero-key video formula: fix rendering bugs, add 8 demo compositions, update skills

Fix ComparisonCard and CalloutBox dark-theme passthrough in SceneRenderer.
Add 8 demo-props JSON files (3 fixed originals + 5 new compositions).
Update scene-director and compose-director skills with all 10 Remotion
scene types and zero-key rendering guidance. Document the proven
all-dark-background formula in remotion.md. Add cinematic renderer,
onboarding skill, prompt gallery, and demo render script.

remotion-composer/src/cinematic/fixtures.ts

@@ -0,0 +1,83 @@
+import { staticFile } from "remotion";
+import { CinematicRendererProps } from "./types";
+
+export const signalFromTomorrowWithMusicFixture: CinematicRendererProps = {
+  titleFontSize: 78,
+  titleWidth: 1320,
+  signalLineCount: 18,
+  soundtrack: {
+    src: staticFile(
+      "music/signal-from-tomorrow/cinematic_time_hans_zimmer_style.mp3",
+    ),
+    volume: 0.42,
+    fadeInSeconds: 1.5,
+    fadeOutSeconds: 2.5,
+  },
+  scenes: [
+    {
+      id: "sc1",
+      kind: "video",
+      startSeconds: 0,
+      durationSeconds: 4,
+      src: staticFile("video/signal-from-tomorrow/sample_observatory_veo31_ref.mp4"),
+      tone: "cold",
+      trimBeforeSeconds: 1,
+      fadeInFrames: 0,
+    },
+    {
+      id: "sc2",
+      kind: "video",
+      startSeconds: 4,
+      durationSeconds: 4,
+      src: staticFile(
+        "video/signal-from-tomorrow/sc2_mission_control_veo31_ref_8s.mp4",
+      ),
+      tone: "steel",
+    },
+    {
+      id: "sc3",
+      kind: "title",
+      startSeconds: 8,
+      durationSeconds: 3,
+      text: "YESTERDAY, THEY LAUNCHED.",
+      accent: "#89d7ff",
+      intensity: 1,
+    },
+    {
+      id: "sc4",
+      kind: "video",
+      startSeconds: 11,
+      durationSeconds: 7,
+      src: staticFile("video/signal-from-tomorrow/sc4_launch_departure_veo31_ref.mp4"),
+      tone: "cold",
+    },
+    {
+      id: "sc5",
+      kind: "title",
+      startSeconds: 18,
+      durationSeconds: 3,
+      text: "THE SIGNAL CAME FROM EARTH.",
+      accent: "#a6e6ff",
+      intensity: 1.15,
+    },
+    {
+      id: "sc6",
+      kind: "video",
+      startSeconds: 21,
+      durationSeconds: 6,
+      src: staticFile(
+        "video/signal-from-tomorrow/sc6_orbital_paradox_veo31_ref_8s.mp4",
+      ),
+      tone: "void",
+    },
+    {
+      id: "sc7",
+      kind: "title",
+      startSeconds: 27,
+      durationSeconds: 3,
+      text: "SIGNAL FROM TOMORROW",
+      accent: "#d6f1ff",
+      intensity: 0.9,
+    },
+  ],
+};

remotion-composer/src/cinematic/types.ts

@@ -13,6 +13,8 @@ export interface CinematicVideoScene extends CinematicBaseScene {
   trimBeforeSeconds?: number;
   trimAfterSeconds?: number;
   filter?: string;
+  fadeInFrames?: number;
+  fadeOutFrames?: number;
 }
 
 export interface CinematicTitleScene extends CinematicBaseScene {
@@ -24,10 +26,20 @@ export interface CinematicTitleScene extends CinematicBaseScene {
 
 export type CinematicScene = CinematicVideoScene | CinematicTitleScene;
 
+export interface CinematicSoundtrack {
+  src: string;
+  volume?: number;
+  trimBeforeSeconds?: number;
+  trimAfterSeconds?: number;
+  fadeInSeconds?: number;
+  fadeOutSeconds?: number;
+}
+
 export interface CinematicRendererProps {
   [key: string]: unknown;
   scenes: CinematicScene[];
   titleFontSize?: number;
   titleWidth?: number;
   signalLineCount?: number;
+  soundtrack?: CinematicSoundtrack;
 }