fix: support Bedrock API key login

packages/coding-agent/docs/providers.md

@@ -55,6 +55,7 @@ pi
 | DeepSeek | `DEEPSEEK_API_KEY` | `deepseek` |
 | NVIDIA NIM | `NVIDIA_API_KEY` | `nvidia` |
 | Google Gemini | `GEMINI_API_KEY` | `google` |
+| Amazon Bedrock | `AWS_BEARER_TOKEN_BEDROCK` | `amazon-bedrock` |
 | Mistral | `MISTRAL_API_KEY` | `mistral` |
 | Groq | `GROQ_API_KEY` | `groq` |
 | Cerebras | `CEREBRAS_API_KEY` | `cerebras` |
@@ -170,6 +171,8 @@ export AZURE_OPENAI_DEPLOYMENT_NAME_MAP=gpt-4=my-gpt4,gpt-4o=my-gpt4o
 
 ### Amazon Bedrock
 
+Use `/login amazon-bedrock` to store a Bedrock API key, or configure one of the ambient AWS credential sources below:
+
 ```bash
 # Option 1: AWS Profile
 export AWS_PROFILE=your-profile