Adds -fit-test copies of the labdesign and messaging decks that apply
container-query font sizing (option 5) and a max-height cap on mermaid
SVGs (option 4) so we can compare overflow behavior side-by-side
against the originals.
Includes a comment explaining why option 2 (custom canvas size) cannot
be demoed inline and would require registering a custom theme via
marp.config.mjs.
Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>
