llms/ollama: WithThink 没有效果 — think 在 "options" 中被序列化 (API 期望为顶级对象) 且忽略空值时会返回 false

Two independent defects in the Ollama integration make `WithThink` (and, on current main, the `ThinkingMode`-derived `Think` flag) a silent no-op.