Reasoning effort + larger tool descriptions
- addedreasoning field on POST /v1/responses — { effort: "minimal" | "low" | "medium" | "high" } toggles extended thinking. Omitted or "minimal" keeps thinking off (default). "low" / "medium" / "high" turn it on, and the chain-of-thought is returned alongside the answer.
- changedPer-tool description hard limit raised from 1 KiB to 16 KiB so callers can embed real per-tool docs (full instructions, schema notes, examples) without us 400ing the request. Name limit unchanged at 64 chars; up to 128 tools per request.