codegen: nicer TypeErrors with -d

[porfbot] Fix splitting with long separators

[porfbot] Fix number predicate semantics

[porfbot] Fix array concat spreadability

[porfbot] Fix string prefix and suffix argument coercion

[porfbot] Fix string padding bounds and allocation

[porfbot] Bounds-check numeric string index reads

[porfbot] Fix UTF-8 string output

[porfbot] Fix update expression coercion

[porfbot] Fix global isNaN coercion

[porfbot] Fix cyclic array stringification

[porfbot] Fix for-of RHS evaluation

[porfbot] Fix substr argument bounds

ci: debug server vs no-server

test262: wip cluster rewrite