Adds the ECS hook issues #43 and #47 named as their real dependency: a
system the *engine* owns, inserted into the frame loop over a component a
game merely declares and carries — no `handler` wired.
- runtime/native/systems.ludic: esys_spriteanim (SpriteAnim frame advance:
loop/once/pingpong) and esys_motion (Motion value tween: linear/in/out/
in-out), both on the by-name reflection ABI, integer + deterministic.
- backend: emit_engine_systems_for_phase inserts the calls after every user
handler in a phase (auto-loop and the drivable tick helpers alike);
uses_engine_systems() drives the systems.ludic splice, the world-table
force-emit, and makes a component-only game count as a systems game.
- A game that declares neither component is byte-for-byte unchanged.
Worked example + regression: examples/library/anim_ecs.ludic. Full suite
73 passed, self-host C-free bootstrap fixpoint intact.
Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>