Search ALL installed skills (including ones not shown in AVAILABLE SKILLS) by keyword. Use this whenever you suspect a fitting skill might exist but is not listed in your system prompt — for example before building a new skill, when the user mentions a domain not covered by visible skills, or after seeing the (N more skills installed) hint. Triggers on phrases like search skills, find a skill for, is there a skill that, 查找skill, 有没有skill做.