Task 378: Standalone Brachistochrone Calculator Page

Status: DONE

Goal

Create a dedicated standalone interactive brachistochrone calculator page at /calculator/ on the site. Currently the calculator is embedded within episode pages — a standalone version allows readers to freely explore transfer physics across all episodes without navigating away from the analysis context.

Features

• All episode presets (EP01-EP05) grouped by episode with labels
• Cross-episode comparison mode (compare two transfers side by side)
• Real-time parameter adjustment with sliders (distance, mass, time, thrust)
• WASM-first calculation with JS fallback
• Verdict badge (plausible/marginal/implausible)
• Educational section explaining the brachistochrone model and assumptions
• Full site navigation integration (linked from "この考証について" dropdown)

Implementation

1. Add renderCalculatorPage() to templates.ts
2. Add build step to build.ts
3. Create calculator-standalone.js module
4. Add nav link in layoutHtml metaLinks
5. Add E2E tests
6. Add content validation tests