feat: Add Agentic Documentation Generation with Repository Context

## 🚀 Feature Request: Agentic Documentation Generation with Repository Context

### Problem Statement
Currently, GitVizz has powerful code analysis and visualization capabilities, but lacks an intelligent, context-aware documentation generation system that can:

- **Automatically generate comprehensive documentation** based on repository structure and code analysis
- **Maintain context awareness** across the entire codebase
- **Adapt documentation style** based on project type and existing patterns
- **Provide interactive documentation** that can answer questions about the code

### Proposed Solution
Implement an **Agentic Documentation Generation System** that leverages the existing GitVizz infrastructure to create intelligent, context-aware documentation.

### Key Features

#### 1. **Smart Documentation Analysis**
- Analyze existing documentation patterns and styles
- Identify undocumented code components
- Detect code structure and relationships using existing graph analysis
- Extract meaningful comments and docstrings

#### 2. **Context-Aware Generation**
- **Repository-wide context**: Understand the entire codebase structure
- **Dependency mapping**: Generate docs that reflect actual code relationships
- **Technology stack awareness**: Adapt documentation style for different frameworks
- **Historical context**: Include evolution of features based on git history

#### 3. **Multi-Format Output**
- **Markdown documentation** for README files and docs
- **API documentation** for backend endpoints
- **Component documentation** for frontend modules
- **Architecture documentation** showing system design

#### 4. **Interactive Documentation Agent**
- **Chat-based documentation**: Ask questions about generated docs
- **Real-time updates**: Reflect code changes in documentation
- **Multi-language support**: Generate docs in multiple languages
- **Custom templates**: Allow organization-specific documentation styles

### Technical Implementation

#### Backend Integration
```python
# New service in backend/utils/
class AgenticDocumentationService:
def __init__(self, repo_analyzer, graph_generator):
self.repo_analyzer = repo_analyzer
self.graph_generator = graph_generator

async def generate_documentation(
self,
repo_path: str,
doc_type: str = "comprehensive",
style: str = "auto"
) -> DocumentationResult:
# Use existing gitvizz_tools for analysis
structure = await self.analyze_code_structure(repo_path)
dependencies = await self.analyze_dependencies(structure)
# Generate context-aware documentation
return await self.create_documentation(structure, dependencies)
```

#### Frontend Components
- **Documentation Generator UI**: New tab in RepoTabs component
- **Interactive Documentation Viewer**: Enhanced documentation.tsx
- **Real-time Documentation Chat**: Integration with existing chat system

#### API Endpoints
```typescript
// New routes in backend/routes/
POST /api/documentation/generate
POST /api/documentation/analyze
GET /api/documentation/status
```

### Integration with Existing Features

#### Leverage Current Capabilities
1. **Code Analysis Tools**: Use existing `analyze_code_structure` and `find_code_quality_issues`
2. **Graph Visualization**: Generate architecture diagrams from dependency graphs
3. **Chat System**: Extend agentic chat for documentation Q&A
4. **Repository Caching**: Cache analysis results for faster regeneration

#### Enhanced GitVizz Tools
Add new tools to `utils/gitvizz_tools.py`:
- `generate_comprehensive_documentation()`
- `analyze_documentation_patterns()`
- `create_api_documentation()`
- `generate_architecture_diagrams()`

### Use Cases

#### 1. **Onboarding New Developers**
- Generate comprehensive project overview
- Create step-by-step setup guides
- Document key architectural decisions

#### 2. **Code Review Support**
- Identify missing documentation
- Suggest documentation improvements
- Generate PR documentation

#### 3. **Project Maintenance**
- Keep documentation in sync with code changes
- Generate release notes
- Create API documentation for external consumers

#### 4. **Educational Content**
- Generate tutorials and examples
- Create code walkthroughs
- Document best practices

### Benefits

- **Time Savings**: Automate documentation creation and maintenance
- **Consistency**: Ensure uniform documentation style across projects
- **Accessibility**: Make complex codebases more approachable
- **Quality**: Reduce documentation drift and outdated information

### Implementation Priority

1. **Phase 1**: Basic documentation generation for code structure
2. **Phase 2**: Context-aware documentation with dependency analysis
3. **Phase 3**: Interactive documentation agent with chat integration
4. **Phase 4**: Multi-format output and custom templates

### Success Metrics

- **Documentation Coverage**: Percentage of code with generated documentation
- **Developer Time Saved**: Reduction in manual documentation effort
- **Documentation Accuracy**: Alignment with actual code functionality
- **User Adoption**: Usage frequency of documentation features

### Related Issues
- Enhancement of existing chat capabilities
- Integration with current graph visualization
- Extension of code analysis tools

### Labels
- `enhancement`
- `documentation`
- `ai`
- `agentic`
- `feature-request`

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**Note**: This feature would build upon the existing agentic chat system (PR #36, #37) and GitVizz analysis tools, creating a comprehensive documentation ecosystem within the platform.