Task 205: Orbital Animation Arrival Alignment Verification & Tests

Status: DONE

Priority: HIGH

Objective

Fix and systematically test orbital animation arrival alignment — destination bodies must be at the correct position when the transfer animation completes.

Problem

• Orbital transfer diagrams show destination bodies that have already moved past the arc endpoint after animation completes
• Cross-episode diagrams have arrival positions that don't match the next episode's departure position
• The current unit tests verify static SVG endpoint alignment but NOT animated body position at arrival time
• No integration test verifies initialAngle + meanMotion * duration == arrivalAngle

Scope

1. Audit all diagrams: Check every orbital diagram's animation data — verify that meanMotion * transferDuration brings each body to its arrivalAngle
2. Add animation arrival test: Test that animated body position at t=transferDuration matches SVG path endpoint within tolerance
3. Cross-episode continuity test: Verify that EP(N) arrival body position == EP(N+1) departure body position
4. Fix misaligned diagrams: Update animation parameters where they're incorrect
5. E2E visual regression: Add Playwright test that captures body positions at animation end

Key Files

• ts/src/orbital-animation.js (browser animation logic)
• ts/src/templates.ts (SVG path generation, animation data embedding)
• ts/src/templates.test.ts (existing alignment tests, lines 4386-4628)
• ts/src/update-diagram-angles.ts (ephemeris → diagram angles)
• ts/src/update-diagram-angles.test.ts (ephemeris validation)
• ts/e2e/examples.spec.ts (E2E animation tests)

Dependencies

• Task 206 (455-day rethink) may change EP02 parameters — coordinate arrival angles accordingly