feat: Add clipboard image pasting with cross-platform support

[prajwalr308]

Summary

Enables users to paste images directly from their clipboard into the Gemini CLI using Ctrl+V or
Shift+Insert. Images are automatically saved to .gemini-clipboard/ directory with sequential
numbering and displayed with clean [image #N] labels that convert to file references when submitted.

This feature provides seamless image sharing across all platforms including macOS, Windows, Linux, and
WSL environments.

Details

Key Features:

• Cross-platform clipboard support: Works on macOS, Windows, Linux, and WSL
• WSL PowerShell integration: Detects WSL environments and uses PowerShell for clipboard access
• Sequential image numbering: Automatically names images as image-1.png, image-2.png, etc.
• Clean UI display: Shows [image #1] in the input, converts to @.gemini-clipboard/image-1.png
  on submit
• Multiple keyboard shortcuts: Supports both Ctrl+V and Shift+Insert
• Format detection: Automatically detects and preserves image formats (PNG, JPG, GIF, BMP, WebP,
  TIFF)
• Auto-cleanup: Removes clipboard images older than 1 hour
• Comprehensive testing: Full test coverage for all clipboard utilities

Implementation:

• New clipboardUtils.ts with clipboard detection and image saving logic
• WSL detection and PowerShell integration for Windows clipboard access
• Enhanced InputPrompt component to handle clipboard paste events
• Added @crosscopy/clipboard package for cross-platform clipboard support
• Image format detection via magic byte analysis

Files Changed:

• packages/cli/src/ui/utils/clipboardUtils.ts - Core clipboard functionality
• packages/cli/src/ui/components/InputPrompt.tsx - UI integration and display format
• packages/cli/src/config/keyBindings.ts - Added Shift+Insert binding
• packages/cli/src/ui/utils/screenshotUtils.ts - Screenshot utilities
• Test files with comprehensive coverage

Related Issues

How to Validate

On macOS/Linux:

1. Copy an image to clipboard (screenshot, browser image, etc.)
2. Run npm run dev or npx @google/generative-ai-cli
3. Press Ctrl+V or Shift+Insert in the input prompt
4. Verify [image #1] appears in the input
5. Submit the prompt and verify the image is sent to Gemini
6. Check .gemini-clipboard/image-1.png exists

On Windows (native):

1. Copy an image to clipboard
2. Run the CLI via npm run dev or npx
3. Press Ctrl+V and verify image paste works
4. Verify sequential numbering with multiple images

On WSL:

1. Copy image in Windows (e.g., Snipping Tool, browser)
2. Open WSL terminal and run the CLI
3. Press Ctrl+V in the CLI
4. Verify PowerShell bridge correctly retrieves Windows clipboard image
5. Check that .gemini-clipboard/image-N.png is created in WSL filesystem

Test sequential numbering:

1. Paste multiple images one after another
2. Verify they're numbered [image #1], [image #2], [image #3], etc.
3. Delete one and paste again - should use next sequential number

Test cleanup:

1. Create old test images with past timestamps in .gemini-clipboard/
2. Paste a new image (triggers cleanup)
3. Verify old images are removed

Pre-Merge Checklist

• Updated relevant documentation and README (if needed)
• Added/updated tests (comprehensive test coverage added)
• Noted breaking changes (if any) - No breaking changes
• Validated on required platforms/methods:
  • MacOS
    • npm run
    • npx
    • Docker
    • Podman
    • Seatbelt
  • Windows
    • npm run
    • npx
    • Docker
  • Linux
    • npm run
    • npx
    • Docker\

[google-cla]

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[SandyTao520]

Hey tests are failing, could you take a look and fix them?