Function detectProviderByModel

detectProviderByModel(model: string): ProviderId | null
Detect provider from a model name using signature matching.

Supports multiple signatures per provider to handle model naming variations:
- OpenAI: gpt-, o1-, o3-, chatgpt-
- Anthropic: claude-*
- xAI: grok-*
Parameters
- model: string
  Model identifier (e.g., "gpt-4", "o1-preview", "claude-3-opus", "grok-2")
Returns ProviderId | null
Provider ID if detected, null otherwise
Example
```
detectProviderByModel('gpt-4-turbo');     // 'openai'
detectProviderByModel('o1-preview');      // 'openai'
detectProviderByModel('o3-mini');         // 'openai'
detectProviderByModel('claude-3-opus');   // 'anthropic'
detectProviderByModel('grok-2');          // 'xai'
detectProviderByModel('unknown-model');   // null
```
- Defined in providers/detection.ts:106