feat: Add screenshot capabilities with optimized defaults

[NakaokaRei]

Summary

• Implements screenshot functionality as requested in Feature: Add screenshot capabilities #14
• Adds three new tools: captureScreen, captureRegion, and saveScreenshot
• Optimized for use with Claude and other LLM tools to prevent timeouts

Changes

New Tools

1. captureScreen: Captures entire screen as base64 JPEG
2. captureRegion: Captures specific screen area as base64 JPEG
3. saveScreenshot: Saves screenshot to file (supports PNG/JPEG)

Key Features

• JPEG compression with quality parameter (default: 0.1)
• Image scaling with scale parameter (default: 0.25)
• Optimized image processing for fast performance
• Comprehensive test coverage

Default Settings

• 10% JPEG quality + 25% scale = ~95% size reduction
• Prevents MCP timeouts when processing large screens
• Typical output: 10-30KB for standard displays

Test Plan

• Unit tests for all screenshot tools
• Error handling for missing parameters
• Quality and scale parameter validation
• File format detection for saveScreenshot
• Manual testing with Claude Desktop app
• Performance testing with large displays

Usage Examples

// Capture full screen with defaults
{"tool": "captureScreen"}

// Capture with higher quality
{"tool": "captureScreen", "arguments": {"quality": 0.5, "scale": 0.5}}

// Capture specific region
{"tool": "captureRegion", "arguments": {"x": 100, "y": 100, "width": 800, "height": 600}}

// Save to file
{"tool": "saveScreenshot", "arguments": {"filename": "screenshot.jpg"}}

Closes #14

🤖 Generated with Claude Code