[Bug] Ollama adapter health check always returns 'health_check_not_supported'

[ryuknull]

Description

The health check for the Ollama provider connection consistently reports healthy: false with the error health_check_not_supported. This occurs even when the provider is correctly configured and the underlying service is available.

Observations

In the /health endpoint response:

"providers": [
  {
    "id": "...",
    "healthy": false,
    "last_error": "health_check_not_supported"
  }
]

Expected Behavior

The gateway should be able to perform a basic "ping" or health check to verify the provider connection status instead of failing by default.

[linear-code]

DALLAY-407