[FEATURE]: Show provider name in assistant message headers #34480

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Describe the enhancement you want to request

When using multiple providers (Anthropic, OpenAI, OpenRouter, custom proxies, etc.), it's hard to tell which provider generated each response. The prompt footer already shows the current provider, but assistant message headers only show the model name — not which provider was hit.

Proposed change: Show the provider name alongside the model name in each assistant message header, with a command-palette toggle to show/hide it (default: shown). This helps users who switch providers frequently trace which provider produced each response.