[FEATURE]: show the provider and model id in message footers #53638

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Describe the enhancement you want to request

Assistant message footers name the model by its display name only: ▣ Build · Claude Opus 4.5 · 29.0s. When the same model is reachable through more than one provider (openai and an OpenAI-compatible gateway clone, a direct API key and a proxy, two Anthropic accounts), every turn reads the same, and nothing on screen says which provider answered it. The prompt's model indicator shows the provider's display name, but that is the current selection, not the turn's, and two custom providers can share a display name too.

Proposal: a model_label setting in tui.json:

• "name" (default): today's display names, unchanged.
• "id": the providerID/modelID the turn actually ran on, e.g. anthropic/claude-opus-4-5 or openai-gateway/gpt-5.5, in every assistant message footer, and in the prompt's model indicator in place of the model and provider names.

// tui.json
{ "model_label": "id" }

Variant, duration and everything else on those lines stay as they are. The ID is the same string /models, --model and opencode.json's model use, so what the footer shows can be pasted straight into config.