Slice 1 of Phase C.1.5: fire Setup.DefaultScript through the already-
shipped PhysicsScriptRunner on server-spawned WorldEntity create, so
portals (and any other entity with a DefaultScript) emit their retail-
faithful persistent particle effects at spawn time. Reuses the C.1
runner-sink-system-renderer chain end-to-end; one new ~50-line class
(EntityScriptActivator) plus a two-line wiring in GameWindow.
Slice 2 (C.1.5b) will cover EnvCell.StaticObjects + animation-hook
verification; spec landed separately after slice 1 verification passes.
Acceptance: visual confirmation at the Holtburg Town network portal,
side-by-side with retail.
Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>