fix: offset nested template video timing (#2859)

* fix: offset nested template video timing

* test(producer): cover nested sequential video render

* fix: share canonical nested media timing

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

@@ -5,6 +5,7 @@ import {
   formatSnapshotTimestamp,
   parseZoomScale,
   requireSnapshotFfmpeg,
+  resolveSnapshotVideoClipStart,
   resolveSnapshotVideoFrameTime,
   tailFrameTime,
 } from "./snapshot.js";
@@ -154,6 +155,35 @@ describe("resolveSnapshotVideoFrameTime", () => {
   });
 });
 
+describe("resolveSnapshotVideoClipStart", () => {
+  it("offsets a scene-local video start by its later template host", () => {
+    expect(
+      resolveSnapshotVideoClipStart({
+        authoredStart: 0,
+        runtimeResolvedStart: 3,
+      }),
+    ).toBe(3);
+  });
+
+  it("uses the runtime's recursively resolved start for deeply nested media", () => {
+    expect(
+      resolveSnapshotVideoClipStart({
+        authoredStart: 1,
+        runtimeResolvedStart: 8,
+      }),
+    ).toBe(8);
+  });
+
+  it("keeps authored starts as a compatibility fallback", () => {
+    expect(
+      resolveSnapshotVideoClipStart({
+        authoredStart: 3,
+        runtimeResolvedStart: null,
+      }),
+    ).toBe(3);
+  });
+});
+
 describe("computeSnapshotTimes (FINDING [7]: tail is always captured)", () => {
   it("default frames: last point is the readable tail, never exact duration", () => {
     const { times, appendedTail } = computeSnapshotTimes(8, { frames: 5 });