feat(ai): add Kimi For Coding provider support

- Add kimi-coding provider using Anthropic Messages API
- API endpoint: https://api.kimi.com/coding/v1
- Environment variable: KIMI_API_KEY
- Models: kimi-k2-thinking (text), k2p5 (text + image)
- Add context overflow detection pattern for Kimi errors
- Add tests for all standard test suites

packages/ai/src/env-api-keys.ts

@@ -107,6 +107,7 @@ export function getEnvApiKey(provider: any): string | undefined {
 		"minimax-cn": "MINIMAX_CN_API_KEY",
 		huggingface: "HF_TOKEN",
 		opencode: "OPENCODE_API_KEY",
+		"kimi-coding": "KIMI_API_KEY",
 	};
 
 	const envVar = envMap[provider];