fix(studio,runtime,engine,compiler): 8 bug fixes — audio, render, timeline, Lottie, thumbnails, video render (#133)

## Summary

**Original 5 bugs fixed:**

- **Bug 1 — Audio silent after seek**: Added `Accept-Ranges` / `Content-Length` + `206 Partial Content` to the static asset server for byte-range seeking.
- **Bug 2 — Download 404 after restart**: Render list endpoint now registers on-disk renders into the in-memory job map.
- **Bug 3 — Timeline stops at GSAP end**: `resolveRootTimelineFromDocument` pads the GSAP timeline to match `data-duration` when the composition declares longer.
- **Bug 4 — Render stuck at 0%**: Store `jobState` reference (not spread copy) so async progress mutations reach the SSE stream.
- **Bug 5 — Lottie missing in preview/render**: Two fixes — (a) moved Lottie adapter before GSAP so `onUpdate` wins; (b) fixed bundler silently dropping external CDN `\<script src>` tags from sub-compositions (root cause: `$content(s).html()` returns `""` for external scripts).

**3 additional bugs fixed:**

- **Bug 6 — Blank thumbnails outside monorepo**: Implemented `generateThumbnail` in the CLI adapter using Puppeteer.
- **Bug 7 — Video empty in rendered sub-compositions**: Fixed `parseVideoElements` selector from `video[id][src]` to `video[src][data-start]` + auto-assign IDs.
- **Render errors**: Failed renders now show their error message in the renders panel.

## Commits

| Commit | Description |
| --- | --- |
| `3951c6f` | fix(studio): store render job reference instead of snapshot copy |
| `f331c30` | fix(studio): make previously-completed renders downloadable after restart |
| `a5e2d04` | fix(studio): add range request support for audio/video seeking in preview |
| `f24317a` | fix(runtime): pad GSAP timeline to data-duration when composition declares longer duration |
| `7cf38ca` | fix(runtime): fix Lottie adapter conflicting with GSAP-driven animations |
| `bc99209` | fix(studio): surface render error messages in the renders panel |
| `8fc9e8b` | fix(cli): implement generateThumbnail in studio adapter |
| `90277ea` | fix(engine): render videos inside sub-compositions that lack an explicit id |
| `f5bb579` | fix(compiler): preserve external CDN scripts from sub-compositions in bundle |

## Test plan

- [x] `golden-lyric-video`: seek → audio plays from seeked position
- [x] Any project: render → progress advances past 0%, reaches 100%
- [x] Any project: complete render, restart `hyperframes dev`, Download → works
- [x] `intro-vid`: play → runs full 5s (not stopping at 3s)
- [x] `hyperframe-build-up-demo`: play → rocket Lottie visible during 0-2s ✅ verified
- [x] Outside monorepo: Compositions sidebar shows thumbnail images (not blank)
- [x] `bug.zip` project: render → video in polaroid sub-composition appears in output
- [x] Trigger a failed render → error message shown

packages/core/src/compiler/htmlBundler.ts

@@ -390,6 +390,7 @@ export async function bundleToSingleHtml(
   // Inline sub-compositions
   const compStyleChunks: string[] = [];
   const compScriptChunks: string[] = [];
+  const compExternalScriptSrcs: string[] = [];
   $("[data-composition-src]").each((_, hostEl) => {
     const src = $(hostEl).attr("data-composition-src");
     if (!src || !isRelativeUrl(src)) return;
@@ -416,9 +417,18 @@ export async function bundleToSingleHtml(
       $content(s).remove();
     });
     $content("script").each((_, s) => {
-      compScriptChunks.push(
-        `(function(){ try { ${$content(s).html() || ""} } catch (_err) { console.error('[HyperFrames] composition script error:', _err); } })();`,
-      );
+      const externalSrc = ($content(s).attr("src") || "").trim();
+      if (externalSrc) {
+        // External CDN/remote script — collect for deduped injection into the document.
+        // Do NOT try to inline the content (external scripts have no innerHTML).
+        if (!compExternalScriptSrcs.includes(externalSrc)) {
+          compExternalScriptSrcs.push(externalSrc);
+        }
+      } else {
+        compScriptChunks.push(
+          `(function(){ try { ${$content(s).html() || ""} } catch (_err) { console.error('[HyperFrames] composition script error:', _err); } })();`,
+        );
+      }
       $content(s).remove();
     });
 
@@ -439,6 +449,14 @@ export async function bundleToSingleHtml(
     $(hostEl).removeAttr("data-composition-src");
   });
 
+  // Inject external scripts from sub-compositions (e.g., Lottie CDN)
+  // that aren't already present in the main document.
+  for (const extSrc of compExternalScriptSrcs) {
+    if (!$(`script[src="${extSrc}"]`).length) {
+      $("body").append(`<script src="${extSrc}"></script>`);
+    }
+  }
+
   if (compStyleChunks.length) $("head").append(`<style>${compStyleChunks.join("\n\n")}</style>`);
   if (compScriptChunks.length)
     $("body").append(`<script>${compScriptChunks.join("\n;\n")}</script>`);