When a user sets `agents.defaults.model.primary: "ollama/gemma3:4b"`
but forgets to set OLLAMA_API_KEY, the error is a confusing
"unknown model: ollama/gemma3:4b". The Ollama provider requires any
dummy API key to register (the local server doesn't actually check it),
but this isn't obvious from the error.
Add `buildUnknownModelError()` that detects known local providers
(ollama, vllm) and appends an actionable hint with the env var name
and a link to the relevant docs page.
Before: Unknown model: ollama/gemma3:4b
After: Unknown model: ollama/gemma3:4b. Ollama requires authentication
to be registered as a provider. Set OLLAMA_API_KEY="ollama-local"
(any value works) or run "openclaw configure".
See: https://docs.openclaw.ai/providers/ollamaCloses#17328
4df970d711