Make interactive demos easier to explore and compare

[jverbus]

The three demos now place their main result beside the interaction: IF/EIF has a linked numerical probe and explicit editing tools, orbital transfers show the predicted coast orbit and retain completed-flight comparisons, and LUX adds angle presets, immediate energy readouts and a brief illustrative neutron traversal.

This also corrects LUX's drawing/physics aspect mismatch, clipped orbit burn histories, IF first-point feedback and touch editing, and animation/lazy-layout edge cases. Model details stay in disclosure elements; the demos remain dependency-free and preserve their no-JavaScript fallbacks.

Validation:

• 99 Node checks pass, including independent physics/algorithm checks and coast stability.
• 60 local Chrome checks pass across desktop, emulated touch/mobile, light/dark themes, keyboard controls, reduced motion and no-JavaScript behavior.
• CI-config and production Jekyll builds, OG metadata and generated-site validators pass; generated-checker output matches the baseline.
• Castle's source, assets, article and metadata are unchanged, with four matching baseline/current screenshot pairs.

Review notes, screenshots and reproducible browser harness. Mobile checks use Chrome emulation; physical iOS/Safari rendering has not been verified.

Draft for owner rendering review before merge.