feat: add Grok/XAI support to the LLM abstraction

- Created XAI provider implementation

- Updated provider registry and configuration

- Added tests and documentation

Closes #148

Author: bhouston

docs/grok-integration.md

@@ -0,0 +1,90 @@
+# Grok/XAI Integration
+
+MyCoder supports [Grok](https://grok.x.ai/) models from xAI as an alternative to Anthropic's Claude models.
+
+## Configuration
+
+To use Grok models, you need to:
+
+1. Set your XAI API key
+2. Configure MyCoder to use the xai provider
+3. Specify a Grok model
+
+### Setting Your XAI API Key
+
+```bash
+mycoder config set XAI_API_KEY your-xai-api-key
+```
+
+Alternatively, you can set the `XAI_API_KEY` environment variable:
+
+```bash
+export XAI_API_KEY=your-xai-api-key
+```
+
+### Configuring the Provider
+
+To use Grok as your default provider:
+
+```bash
+mycoder config set provider xai
+```
+
+### Selecting a Grok Model
+
+MyCoder supports various Grok models:
+
+```bash
+# For Grok 2
+mycoder config set model grok-2-1212
+
+# For Grok 2 with vision capabilities
+mycoder config set model grok-2-vision-1212
+
+# For other available models
+mycoder config set model grok-beta
+mycoder config set model grok-vision-beta
+```
+
+## Using Grok for a Single Command
+
+You can also use Grok for a single command without changing your default configuration:
+
+```bash
+mycoder --provider xai --model grok-2-1212 "Your prompt here"
+```
+
+## Features
+
+The Grok integration supports all MyCoder features, including:
+
+- Tool usage for complex operations
+- Sub-agent spawning for parallel tasks
+- GitHub mode for working with issues and PRs
+- All file and shell operations
+
+## Troubleshooting
+
+If you encounter issues with the Grok integration, check the following:
+
+1. Ensure your API key is correct and has sufficient permissions
+2. Verify that you're using a valid model name
+3. Check that your account has access to the specified model
+4. Ensure your API key has not expired or been revoked
+
+For more detailed logs, run MyCoder with increased verbosity:
+
+```bash
+mycoder --logLevel debug "Your prompt here"
+```
+
+## Comparing Models
+
+Different models have different strengths:
+
+- **grok-2-1212**: General-purpose model with strong coding capabilities
+- **grok-2-vision-1212**: Supports image processing in addition to text
+- **grok-beta**: Earlier version of Grok, may be more suitable for simpler tasks
+- **grok-vision-beta**: Earlier vision-capable model
+
+Experiment with different models to find the one that works best for your specific use case.