A schema nesting arrays past ~200 levels rendered a `list[list[...]]` chain
CPython's tokenizer rejects outright (`too many nested parentheses`), so the
SDK block was not valid Python at all — the failure docstring escaping in the
same file already guards against. The chain now degrades to `Any` at 180
levels; nesting restarts per TypedDict field, since a field annotation is its
own logical line. Unions and nested objects are unaffected: neither
accumulates open brackets.
Also aligns the unreachable SDK_RENDERERS guard message with the two reachable
ones, and corrects a test comment that still said class docstring.
95da760696