pi-ai 0.85.1 runs parseStreamingJson over the whole accumulated argument
JSON on every tool-call delta, so one large tool call costs O(n²) CPU on
the event loop and a multi-megabyte argument stream stalls every session
in the process. Patch the six stream adapters to parse once at
toolcall_end, document the patch, and cover both OpenAI protocols.
Fixes#4739
