docs: Create comprehensive troubleshooting guide for common ADK errors

## Summary

This issue proposes creating a comprehensive troubleshooting guide in the adk-docs repository to help developers quickly resolve common ADK errors and configuration issues.

## Problem Statement

While ADK provides helpful error messages when tools or agents are not found, developers would benefit from a centralized troubleshooting resource that covers the full spectrum of common issues encountered during ADK development.

## Proposed Solution

**Create**: `adk-docs/docs/troubleshooting/common-errors.md`

## Proposed Content Structure

### 1. **Tool and Agent Errors**
- Tool not found scenarios and resolution steps
- Agent configuration and lookup issues
- Type annotation problems with function tools
- Tool execution failures and debugging

### 2. **Configuration Issues**
- Environment variable setup
- Model configuration and authentication
- Service startup and port conflicts
- Project structure and dependency issues

### 3. **Integration Challenges**
- AG-UI middleware integration patterns
- Session state and memory management
- Multi-agent orchestration problems
- A2A protocol setup and debugging

### 4. **Performance and Optimization**
- Tool execution timeouts and resolution
- Memory usage optimization techniques
- Parallel execution configuration
- Long-running tool best practices

### 5. **Development Workflow Issues**
- Testing setup and common test failures
- Deployment configuration problems
- Streaming and real-time operation issues
- Debugging techniques and tools

## User Benefits

1. **Faster Problem Resolution**: Centralized troubleshooting reduces time spent searching across multiple docs
2. **Self-Service Debugging**: Developers can resolve common issues independently
3. **Better Developer Experience**: Clear step-by-step resolution guides
4. **Reduced Support Load**: Comprehensive documentation handles frequent questions

## Implementation Approach

- **Clear Problem-Solution Format**: Each issue with symptoms, causes, and step-by-step resolution
- **Code Examples**: Working examples of proper configuration and usage patterns
- **Cross-References**: Links to relevant sections in existing documentation
- **Interactive Elements**: Troubleshooting flowcharts where helpful
- **Search-Friendly**: Clear headings and keywords for easy discovery

## Success Criteria

- Covers 80% of common support questions and GitHub issues
- Provides actionable resolution steps for each problem
- Integrates seamlessly with existing adk-docs navigation
- Maintains consistency with ADK documentation style and tone

## Related Documentation

This troubleshooting guide would complement existing ADK documentation:
- Function Tools best practices (error handling)
- Agent configuration guides
- Deployment documentation
- Testing and development setup guides

The guide would serve as a practical companion to the comprehensive ADK documentation, focusing specifically on problem resolution and debugging workflows.

Cheers, JP