Task 261: Adaptive Integration Browser Demo

Status: DONE

Priority: HIGH

Objective

Create an interactive browser demo page for the orbital propagation WASM functions (RK45 Dormand-Prince, Störmer-Verlet symplectic, and fixed-step RK4). Of the ~90+ WASM-exported functions, only 8 are used browser-side. This demo addresses the massive export-to-usage gap and fulfills DESIGN.md's requirement for browser-reproducible analysis.

Context

CLAUDE.md: "Each interactive library should have standalone example HTML pages"
DESIGN.md: "wasm にビルドしてレポートでの再現が可能になるようにすること"
Existing example pages: ts/examples/ (orbital-animation, uplot-chart, dag-viewer, duckdb-explorer, bar-chart)
WASM propagation exports: propagate_ballistic, propagate_brachistochrone, propagate_trajectory, propagate_adaptive_ballistic, propagate_adaptive_brachistochrone, propagate_symplectic_ballistic
Also ephemeris: planet_position, planet_longitude, etc.

Scope

Standalone HTML example page: ts/examples/propagation-demo.html
Browser JS module: ts/src/propagation-demo.js
Features:

- Select integrator (RK4, RK45, Störmer-Verlet)

- Configure initial conditions (preset scenarios from episode transfers)

- Visualize trajectory in 2D SVG

- Compare integrator accuracy (energy drift) and step counts

- Show planetary orbits as reference

E2E test for the demo page
Build pipeline integration (copy JS + HTML to dist)

Remaining Work

See scope above

Acceptance Criteria

[ ] Demo page loads and renders without errors
[ ] All three integrators work and produce visible trajectories
[ ] Energy drift comparison shows numeric values
[ ] Episode preset scenarios load correctly
[ ] E2E test passes
[ ] Existing tests remain green