Enhance math curriculum content and improve rendering: Update contributing guidelines for math widget integration and clarify KaTeX usage. Add interactive demo technology choices to SKILL.md for better guidance on chapter interactions. Introduce new visual elements in coordinate geometry chapters, including an empty Cartesian plane SVG and detailed proofs for distance, midpoint, and slope formulas. Revise Pythagorean theorem content to include geometric proofs and applications, enhancing clarity and educational value.

.agents/skills/ofb/SKILL.md

@@ -135,6 +135,18 @@ Live chapters live under `content/{subject}/{slug}/`:
 
 **Math checkpoints / dots:** follow [math-chapter-patterns.md](math-chapter-patterns.md); shared dot classes in `content/math/subject.scss`.
 
+### Interactive demo technology choices
+
+Interactive demos can use different technologies based on the learning goal and interaction type:
+
+- **Vanilla JavaScript / Solid widget**: default for lightweight chapter interactions and custom canvas/SVG behavior.
+- **JSXGraph**: geometric constructions (points, lines, labeled angles, right-angle markers, draggable Euclidean figures).
+- **Plotly.js**: data-heavy charts, coordinate plots, and quick interactive graphing.
+- **D3**: custom data visualizations where fine-grained control over rendering/animation is needed.
+- **three.js**: 3D scenes, spatial intuition demos, and rotation/perspective interactions.
+
+Choose the simplest tool that satisfies the pedagogy, performance, and accessibility needs of the chapter.
+
 Reference: `content/math/quadratic-equations/`.
 
 ## Verify before PR