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.ts

@@ -14,6 +14,31 @@ export function formatDuration(ms: number): string {
   return `${minutes}m ${remaining.toFixed(1)}s`;
 }
 
+/**
+ * Build the detail portion of the render-complete summary (everything after the
+ * file size). The output video length is shown as the primary figure, with the
+ * wall-clock render time explicitly labeled "rendered in" so the two are never
+ * confused (users were comparing the render time to ffprobe's media duration).
+ * Directory (png-sequence) output has no single muxed video, so it shows a frame
+ * count instead, or just the render time when neither is known.
+ */
+export function formatRenderSummaryDetail(input: {
+  elapsedMs: number;
+  outputDurationSeconds?: number;
+  isDirectory: boolean;
+  frameCount?: number;
+}): string {
+  const middle = input.isDirectory
+    ? input.frameCount != null
+      ? `${input.frameCount} frames`
+      : undefined
+    : input.outputDurationSeconds != null && input.outputDurationSeconds > 0
+      ? `${formatDuration(input.outputDurationSeconds * 1000)} video`
+      : undefined;
+  const renderTime = `rendered in ${formatDuration(input.elapsedMs)}`;
+  return [middle, renderTime].filter(Boolean).join(" · ");
+}
+
 export function label(name: string, value: string): string {
   const pad = 14 - name.length;
   return `   ${c.dim(name)}${" ".repeat(Math.max(1, pad))}${c.bold(value)}`;