feat: equation layout for mathematical-style graphics

[gregmeyer]

Summary

• New equation layout type that renders equations as stacked, typographically rich graphics
• Parses equation strings into terms and operators automatically (=, +, −, ×, ÷)
• Supports both CSS (default) and Pretext SVG text rendering modes
• Designed for social media graphics where the equation IS the visual content

Usage

CLI:

modern-graphics create --layout equation \
  --equation "Satisfaction = Perception - Expectation" \
  --eq-label "The Satisfaction Gap" \
  --footnote "The gap is where churn lives." \
  --theme dark --png

MCP:

{"layout": "equation", "theme": "dark", "args": {"equation": "Satisfaction = Perception - Expectation", "label": "The Satisfaction Gap", "footnote": "The gap is where churn lives."}}

Test plan

• CSS mode renders stacked equation with operators aligned left
• Pretext mode renders with SVG text slots
• Dark theme: white text on dark gradient, blue operators
• Apple theme: dark text on light background, blue operators
• Multi-operator equation (Revenue = Volume × Price − Cost) parses correctly
• All 51 smoke tests pass

🤖 Generated with Claude Code