Embed annotate.py module in image-annotations skill

The full working module (annotate_image, grid_image, diff_images) is now
included as a code block so users can save it as annotate.py and import
directly. Scrubbed project-specific labels from examples.

Co-authored-by: Copilot <223556219+Copilot@users.noreply.github.com>

Author: nohwnd