Changes ```dot to ```graphviz across all docs for better syntax highlighting
in Mintlify (Shiki). Full digraph blocks get a title derived from the workflow
name (e.g. title="hello.dot").
Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>
Add Backends section to agents page explaining the two execution
strategies, expand backend attribute descriptions in dot-language
and stylesheet references, and add API-only notes to tools and
sub-agents pages.
Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>