Initial release of moss-deep-search (deep-search) skill.

- Enables deep web research using multiple search rounds and LLM analysis.
- Triggered by requests for comprehensive, detailed search or analysis (e.g., "deep search", "详细搜索", "深入调查").
- Analyzes queries, iteratively searches (3–5 rounds), aggregates and reports findings.
- Outputs include: execution plan, chaptered report, source links, and actionable summary.