fix(cli): show output video length in render summary, not render time (#1812)

The render-complete summary printed `<fileSize> · <time> · completed`
where `<time>` was the wall-clock render duration. Presented as a bare
middle value, users read it as the video length and compared it to
ffprobe, repeatedly reporting a "wrong duration".

Show the actual output video length (from the perf summary's
compositionDurationSeconds, which equals the rendered frame span) as the
primary figure and label the render time explicitly:
`<fileSize> · <videoLength> video · rendered in <renderTime>`.

png-sequence (directory) output has no single muxed video, so it shows a
frame count instead; when neither is known the summary falls back to
render time only. Docker renders run the producer in a child process
with no perf summary threaded back, so they show render time only rather
than a misleading number.

packages/cli/src/ui/format.test.ts

@@ -0,0 +1,42 @@
+import { describe, expect, it } from "vitest";
+
+import { formatRenderSummaryDetail } from "./format.js";
+
+describe("formatRenderSummaryDetail", () => {
+  it("shows the output video length as the primary figure and labels render time", () => {
+    // Output is 71.7s of video but only took 34.2s of wall-clock to render:
+    // the two must be distinguishable so users stop comparing render time to ffprobe.
+    const detail = formatRenderSummaryDetail({
+      elapsedMs: 34_200,
+      outputDurationSeconds: 71.7,
+      isDirectory: false,
+    });
+    expect(detail).toBe("1m 11.7s video · rendered in 34.2s");
+    expect(detail).toContain("video");
+    expect(detail).toContain("rendered in");
+  });
+
+  it("omits the video figure gracefully when the duration is unknown", () => {
+    expect(formatRenderSummaryDetail({ elapsedMs: 5_000, isDirectory: false })).toBe(
+      "rendered in 5.0s",
+    );
+  });
+
+  it("shows a frame count for png-sequence directory output instead of a video length", () => {
+    const detail = formatRenderSummaryDetail({
+      elapsedMs: 12_000,
+      isDirectory: true,
+      frameCount: 120,
+      // a stray duration must not leak into directory output
+      outputDurationSeconds: 4,
+    });
+    expect(detail).toBe("120 frames · rendered in 12.0s");
+    expect(detail).not.toContain("video");
+  });
+
+  it("does not crash and shows only render time for a directory with no frame count", () => {
+    expect(formatRenderSummaryDetail({ elapsedMs: 1_000, isDirectory: true })).toBe(
+      "rendered in 1.0s",
+    );
+  });
+});