feat(ecs): engine-owned systems auto-tick user components (#43)

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>

tools/x/test.ludic

@@ -242,6 +242,11 @@ function cmd_test() -> int {
   net_case("ecs/world_mixed", "99")
   net_case("ecs/world_query", "2 110")
 
+  # #43: engine-owned systems auto-advance the SpriteAnim / Motion components a
+  # game merely declares and carries — no handler wired. Entry-driven so it can
+  # assert the auto-advanced fields at known tick counts.
+  net_case("library/anim_ecs", "1 5 2 10 0 2 10 1 1")
+
   feat_case("events/recurse", "", "16", "recurse.ludic (EV6: re-entrant emit is depth-bounded, no runaway cycle)")
   net_case("events/scoped", "2")
   net_case("ecs/world_dyn", "0 1 30 100 1 30")