* server: align generate with native chat templates
/api/generate rebuilt chat-like prompts through the Go template path even when the model selected its native GGUF Jinja chat template, so the same model rendered differently between generate and chat.
Route chat-like generate requests through the shared native chat preparation path, keep deprecated context and image handling working there, and keep explicit OLLAMA_GO_TEMPLATE overrides intact.
Fixes#16792
* review comments
Fall back to "{{ .Prompt }}" when lacking templates
Daniel Hiltgen