Resolve the render browser from one explicit cache

Resolve the render browser from one explicit cache The hosted render failed inside the browser launcher while the local run passed. The install and render steps each resolved a default cache path, so pin one workspace cache for both. The failure was also unreadable: only the last 1000 characters of stderr were kept, which is stack frames. Keep the head instead, where the message is. Co-Authored-By: Claude Opus 5 (1M context) Claude-Session: https://claude.ai/code/session_01XmzqahsmAXBn5wJab92jP2