fix(cli): never print "[object Object]" from validate/inspect errors (#1810)

* fix(cli): use normalizeErrorMessage so validate/inspect never print "[object Object]"

The validate and inspect (layout) commands formatted thrown values with
`err instanceof Error ? err.message : String(err)`. When a browser/CDP/
Puppeteer protocol error or a structured page error reaches the formatter
as a plain object without a string `message`, `String(obj)` yields the
useless literal "[object Object]", hiding the real cause.

Route those paths through the existing shared `normalizeErrorMessage`
helper, which returns an Error's message, a string as-is, an object's
`.message` when present, or a compact JSON serialization otherwise (with
a key-list and String fallback for circular/opaque objects). Also fold
the duplicated local `errorMessage` helpers in batchRender and preview
into the same shared helper.

Covered by added assertions in errorMessage.test.ts for the no-message
object and Puppeteer-style protocol-error object cases.

* fix(cli): route remaining browser/process error sites through normalizeErrorMessage

The validate/inspect fix routed only those two commands through the shared
normalizeErrorMessage helper. The same err instanceof Error ? err.message :
String(err) pattern survived in the other commands that drive a headless
browser or an external process (ffmpeg, Docker, CDP) or surface a network
API error, so a thrown structured object without a string message would
still render as the useless literal [object Object].

Route those sites through the shared helper:
  snapshot.ts (the closest sibling to validate/inspect, same bug class),
  render.ts (Chrome launch + Docker build), capture/index.ts and
  commands/capture.ts (page-driven extraction), auth/browser.ts,
  browser/manager.ts (Puppeteer browser resolution), and the cloud/lambda
  paths (cloud/render.ts, cloudrun.ts, lambda/render-batch.ts,
  lambda/policies.ts, cloud/detectAspectRatio.ts) that surface API/network
  error objects.

Only the message-deriving expression changes; control flow and error
propagation are untouched. capture/index.ts keeps appending the stack for
real Errors and only routes the non-Error branch. Adds a helper test for a
structured CDP-style error object (code + nested data, no message).

packages/cli/src/cloud/detectAspectRatio.ts

@@ -22,6 +22,7 @@
  */
 
 import { readFileSync } from "node:fs";
+import { normalizeErrorMessage } from "../utils/errorMessage.js";
 
 export type SupportedAspectRatio = "16:9" | "9:16" | "1:1";
 
@@ -87,7 +88,7 @@ export function detectAspectRatioFromHtml(entryHtmlPath: string): AspectRatioDet
   try {
     html = readFileSync(entryHtmlPath, "utf-8");
   } catch (err) {
-    return { kind: "read-error", error: err instanceof Error ? err.message : String(err) };
+    return { kind: "read-error", error: normalizeErrorMessage(err) };
   }
   return detectAspectRatioFromHtmlString(html);
 }