### What happened?

When a spend-log row has no request/response payload, the LiteLLM UI trace view shows:

> **Request/Response Data Not Available** — To view request and response details, enable prompt storage in your LiteLLM configuration by adding the following to your proxy_config.yaml ... `store_prompts_in_spend_logs: true`

This hint is shown even when `store_prompts_in_spend_logs` **is already enabled** and every other request on the same deployment has payloads. The payload can be missing for other reasons — in our case, MCP gateway streaming requests whose internal LLM call failed (see #32561 / #32562) stored a spend-log row with no payload. The banner sent us down a config-debugging rabbit hole while the real problem was a swallowed provider error.

Expected: the UI should distinguish "prompt storage is disabled" (config hint is correct) from "this particular request stored no payload" (config hint is misleading; something failed or was never captured for this request).

### Steps to Reproduce

1. Enable `store_prompts_in_spend_logs: true` (or `STORE_PROMPTS_IN_SPEND_LOGS=true`). 2. Produce a spend-log row without payload (e.g. an MCP gateway streaming request whose init…