feat(storybook): redesign BaseNode Shapes page with doc layout and IA improvements

- Split monolithic Default story into Shapes, Execution States, Sizes
- Rename Dynamic Handles → Handles, canvasLabel resolution → Label Resolution,
  Customized sizes → Sizes for consistency
- Shapes page: Wind-style doc layout with header, full-bleed 80vw canvas
  preview (expand/collapse overlay at 80vw×80vh), shape gallery cards with
  CSS swatches, anatomy spec table, and How to use code block

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

Author: dbacomputer