feat: YC application answers + Remotion video component + gitignore updates

- Add YC_APPLICATION_ANSWERS.md with full Summer 2026 application draft
  (all fields answered, updated with mortgage broker user interview quote)
- Wire OffthreadVideo into YCAppVideo.tsx for founder recording playback
- Ignore .mov files and .gstack/ in .gitignore

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

videos/remotion-demo/src/YCAppVideo.tsx

@@ -1,10 +1,20 @@
-import { AbsoluteFill, interpolate, spring, useCurrentFrame, useVideoConfig } from "remotion";
+import {
+  AbsoluteFill,
+  OffthreadVideo,
+  Sequence,
+  staticFile,
+  interpolate,
+  spring,
+  useCurrentFrame,
+  useVideoConfig,
+} from "remotion";
 import { COLORS, FONT, SPRING_CFG } from "./styles";
 
 // ─── CONFIG ──────────────────────────────────────────────────────────
 const INTRO_DURATION = 3;   // seconds
 const OUTRO_DURATION = 2;   // seconds
 const TOTAL_DURATION = 60;  // seconds (YC wants ~1 min)
+const TALKING_HEAD_DURATION = TOTAL_DURATION - INTRO_DURATION - OUTRO_DURATION;
 
 // ─── INTRO CARD ──────────────────────────────────────────────────────
 const IntroCard = () => {
@@ -126,7 +136,7 @@ const VideoFrame = ({ children }: { children?: React.ReactNode }) => {
   // Fade in from intro
   const fadeIn = interpolate(
     frame,
-    [INTRO_DURATION * fps, (INTRO_DURATION + 0.5) * fps],
+    [0, 0.5 * fps],
     [0, 1],
     { extrapolateLeft: "clamp", extrapolateRight: "clamp" }
   );
@@ -134,7 +144,7 @@ const VideoFrame = ({ children }: { children?: React.ReactNode }) => {
   // Fade out to outro
   const fadeOut = interpolate(
     frame,
-    [(TOTAL_DURATION - OUTRO_DURATION - 0.5) * fps, (TOTAL_DURATION - OUTRO_DURATION) * fps],
+    [(TALKING_HEAD_DURATION - 0.5) * fps, TALKING_HEAD_DURATION * fps],
     [1, 0],
     { extrapolateLeft: "clamp", extrapolateRight: "clamp" }
   );
@@ -328,7 +338,21 @@ export const YCAppVideo = () => {
   return (
     <AbsoluteFill style={{ background: "#000" }}>
       {showIntro && <IntroCard />}
-      {!showIntro && !showOutro && <VideoFrame />}
+      <Sequence
+        from={INTRO_DURATION * fps}
+        durationInFrames={TALKING_HEAD_DURATION * fps}
+      >
+        <VideoFrame>
+          <OffthreadVideo
+            src={staticFile("yc-founder-recording.mov")}
+            style={{
+              width: "100%",
+              height: "100%",
+              objectFit: "cover",
+            }}
+          />
+        </VideoFrame>
+      </Sequence>
       {showOutro && <OutroCard />}
     </AbsoluteFill>
   );