Update release docs to use create-dmg

[Gabko14]

Summary

• Replace bare hdiutil with create-dmg in release docs
• Produces styled DMG with Applications symlink and proper icon layout

Test plan

• Docs-only change

[claude]

Review: LGTM ✓

This is a straightforward documentation improvement that replaces the basic hdiutil command with create-dmg for generating styled DMGs.

Changes reviewed:

• Added dependency note: (requires \brew install create-dmg`)` - helpful for users who may not have the tool installed
• Improved DMG command: The new create-dmg command includes:
  • Window positioning and sizing (--window-pos, --window-size)
  • Icon layout (--icon-size, --icon)
  • Applications folder symlink (--app-drop-link) - this is the standard macOS DMG UX
  • Hidden extension (--hide-extension)

Verification:

• The create-dmg syntax follows the standard format: options → output file → source folder
• Icon positioning (180, 180) and app-drop-link (480, 180) are properly offset within the window size (660x400)

No issues found. This produces a more polished, user-friendly DMG with the drag-to-Applications workflow that macOS users expect.