ImmediateInstall
Folds runtime addons while preserving the stacked type:
Rt & AddonA & AddonB & ....
Every stacked installer is (rt, scheduler) -> rt'. Factories close over
extra config and return that shape:
JecsImmediateInstall(components, DEBUG)
A Lua table { installer, installer } will not produce that megatype:
Luau treats it as an array of a union. Separate arguments keep each
step's From -> To. Use stack1–stack8.
The game alias is typeof(create(...)) of a function that returns the
stackN(...) result. Do not reassign one rt local across installers.