Implement get_repository_file MCP Tool and service

Proposal

Add support for new MCP tool: get_repository_file as a custom tool that enhances the standard Repository Files API - Get file from repository with line range functionality and multiple file support.

Custom Tool Features

• Support for multiple file paths in a single request
• Line range functionality for retrieving specific portions of files
• Intelligent file truncation with helpful prompts for accessing more content
• Custom prompt system to guide users when files are truncated

API Parameters

The custom tool will accept the following parameters:

"file_paths": "Array (required)", 
"line_start": "integer (optional)",
"line_end": "integer (optional)",
"max_lines": "integer (optional, default: 100)"

File Truncation Behavior

When files are truncated, the tool will provide helpful guidance:

File truncated. To view more content, use:
- Lines 101-200: {"line_start": 101, "line_end": 200}
- Lines around specific area: {"line_start": 250, "line_end": 300}
- Remaining lines: 350 lines available

Requirements

• Ensure Duo Context Exclusion is respected for this tool
• Implement custom backend logic to handle line range functionality
• Support array of file paths for batch file retrieval
• Provide intelligent truncation with user-friendly prompts

Technical Notes

Note: Line range functionality exists for git blame but not for file retrieval. This implementation will require custom logic beyond the standard API mapping approach to provide enhanced file access capabilities.