Replace the recursive parseJSONString with an equivalent iterative unwrap.
The recursion re-parsed its own already-parsed result until JSON.parse threw;
on scalar JSON values (e.g. "5" -> 5) that recursed until a stack overflow
which was then silently caught — wasted work on every complete tool-call
payload. The loop returns the identical value in all cases (verified
byte-identical across 29 inputs incl. double/triple-encoded and partial JSON)
without the stack churn.
Co-authored-by: Claude Opus 4.8 <noreply@anthropic.com>
