Model selector shows no models when provider payload omits `cost.cache`

[GammelSami]

The model selector can show an empty list even though providers are connected and /api/opencode/provider returns models.

Root cause

In frontend/src/api/providers.ts (getProvidersFromOpenCodeServer), model mapping assumes openCodeModel.cost.cache.read/write always exists.
Some models (e.g. Google models like gemini-embedding-001) return cost without cache, which throws at runtime.
The outer try/catch then returns an empty provider list.

Reproduce

1. Connect providers (e.g. Google/OpenAI) via WebUI or mounted auth (both reproduce).
2. Open model selection dialog.
3. Ensure /api/opencode/provider includes a model with cost but no cost.cache.
4. Result: no models are shown in UI.

Expected

Missing optional fields in one model should not break the full provider/model list.

Actual

A single malformed/partial model entry causes the whole list to fail and the UI shows no models.

Suggested fix

• Make mapping defensive:
  • cache_read: openCodeModel.cost?.cache?.read ?? 0
  • cache_write: openCodeModel.cost?.cache?.write ?? 0
• Optionally isolate errors per model/provider so one bad entry doesn't drop the entire list.