feat: add Google Gemini provider integration and docs

src/utils/factory.ts

@@ -6,12 +6,13 @@
 import type { AIProviderConfig } from '../types/index.js';
 import { ClaudeProvider, type ClaudeConfig } from '../providers/claude.js';
 import { OpenAIProvider, type OpenAIConfig } from '../providers/openai.js';
+import { GeminiProvider, type GeminiConfig } from '../providers/gemini.js';
 import { BaseAIProvider } from '../providers/base.js';
 
 /**
  * Supported AI provider types
  */
-export type ProviderType = 'claude' | 'openai';
+export type ProviderType = 'claude' | 'openai' | 'gemini';
 
 /**
  * Configuration map for different provider types
@@ -19,6 +20,7 @@ export type ProviderType = 'claude' | 'openai';
 export interface ProviderConfigMap {
   claude: ClaudeConfig;
   openai: OpenAIConfig;
+  gemini: GeminiConfig;
 }
 
 /**
@@ -36,6 +38,8 @@ export function createProvider<T extends ProviderType>(
       return new ClaudeProvider(config as ClaudeConfig);
     case 'openai':
       return new OpenAIProvider(config as OpenAIConfig);
+    case 'gemini':
+      return new GeminiProvider(config as GeminiConfig);
     default:
       throw new Error(`Unsupported provider type: ${type}`);
   }
@@ -73,6 +77,22 @@ export function createOpenAIProvider(
   });
 }
 
+/**
+ * Create a Gemini provider with simplified configuration
+ * @param apiKey - Google AI API key
+ * @param options - Optional additional configuration
+ * @returns Configured Gemini provider instance
+ */
+export function createGeminiProvider(
+  apiKey: string,
+  options: Partial<Omit<GeminiConfig, 'apiKey'>> = {}
+): GeminiProvider {
+  return new GeminiProvider({
+    apiKey,
+    ...options
+  });
+}
+
 /**
  * Provider registry for dynamic provider creation
  */
@@ -122,4 +142,5 @@ export class ProviderRegistry {
 
 // Pre-register built-in providers
 ProviderRegistry.register('claude', ClaudeProvider);
-ProviderRegistry.register('openai', OpenAIProvider); 
+ProviderRegistry.register('openai', OpenAIProvider);
+ProviderRegistry.register('gemini', GeminiProvider);