feat: add video frame format render option (#1481)

* feat: add video frame format render option

* refactor: single source of truth for video-frame-format allow-list

Addresses PR review (Via) on #1481: the ["auto","jpg","png"] set was
declared three times — render.ts (VIDEO_FRAME_FORMATS), server.ts
(inline includes), and renderConfigValidation.ts
(ALLOWED_VIDEO_FRAME_FORMATS) — three boundaries to update when a new
extraction format lands.

Hoist the constant + a reusable `isVideoFrameFormat` type guard into
@hyperframes/engine (where VideoFrameFormat is defined) and route all
three call sites through them. Behavior unchanged; also drops two
`as RenderConfig[...]` casts in favor of the guard (narrowing over
assertion, per repo TS conventions).

Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>

---------

Co-authored-by: Xuelong Mu <xuelongmu@gmail.com>
Co-authored-by: Claude Opus 4.8 (1M context) <noreply@anthropic.com>

packages/cli/src/commands/render.test.ts

@@ -237,6 +237,21 @@ describe("renderLocal browser GPU config", () => {
     expect(producerState.createdJobs[0]?.gifLoop).toBe(3);
   });
 
+  it("forwards videoFrameFormat to createRenderJob", async () => {
+    await renderLocal("/tmp/project", "/tmp/out.mp4", {
+      fps: { num: 30, den: 1 },
+      quality: "standard",
+      format: "mp4",
+      gpu: false,
+      browserGpuMode: "software",
+      hdrMode: "auto",
+      quiet: true,
+      videoFrameFormat: "png",
+    });
+
+    expect(producerState.createdJobs[0]?.videoFrameFormat).toBe("png");
+  });
+
   it("omits variables from createRenderJob when not provided", async () => {
     await renderLocal("/tmp/project", "/tmp/out.mp4", {
       fps: { num: 30, den: 1 },