initial: world-overlay-test v0.1.0 — 23 assertions

Tests all spec-required behaviors: spawn/list, invalid-kind and missing-anchor
validation, ttl expiry via engine.time monkey-patch, despawn idempotency,
entity-anchor position tracking, fixed-anchor snapshot, composite child count,
alpha envelope (mid-hold and fade-out phases), entity-destroyed last_pos
fallback, and rise_px formula verification. 23 pass, 0 fail.

manifest.core

@@ -0,0 +1,6 @@
+{
+    "id": "lib-core.world-overlay-test.core",
+    "kind": "lib",
+    "version": "0.1.0",
+    "license": "Proprietary"
+}