Add bubble chat interface and interaction enhancements

[kxrm]

This adds a floating bubble chat interface for interactive Claude conversations, along with several improvements to the vision tools.

Main changes:

• New bubble.sh tool with a native macOS GUI for displaying messages, pointing at screen elements, and capturing user responses
• Element detection for icons and buttons without text labels (focus-based drag operations)
• --near flag for OCR disambiguation when multiple text matches exist
• Drag operations between coordinates, text, and detected elements
• --point-at for positioning bubbles relative to screen elements
• Image extraction from --read-page output
• Smart image resizing to 1568px for API compatibility
• --preview flag on screenshot.sh to verify click coordinates before executing

The bubble interface uses a lightweight AppKit window that stays on top and can point arrows at specific UI elements, which is useful for guiding users through multi-step tasks.