hardening-a-parser-port

Use when porting or writing a recursive-descent parser, lexer, or tree-walker over untrusted text in the @effected monorepo — the class of hardening the cloud reviewer scans for on every migration. Covers stack-overflow depth guards (on EVERY recursion surface, which a facade has N of — not two), numeric bound guards that must reject NaN and non-integers, code-point range checks scoped to formats with wide escapes, prototype-pollution, control-character rejection, and the invariant that malformed input must fail through the typed error channel, never as an unhandled defect.