Errored tool calls now show in the technical view

When you test an agent in the playground's Technical view or read back a conversation transcript, a tool call that errored and was retried now appears as a collapsed "Used tool" row, the same way a connector (MCP) tool error already did.

Before, one of the assistant's built-in tools (product comparison, product detail, ask a question, product list) could occasionally fail its first call and get re-issued correctly on the next step, but the failed call was dropped from the technical display. The view looked clean even though the assistant had stumbled and recovered. Now you see both the errored call and the retry, so you can tell exactly what the agent did.

This only affects the technical, behind-the-scenes displays used for reviewing agents. The shopper-facing view (the public embed and the playground's Shopper view) is unchanged: a real shopper still never sees a technical error.