Semantic code search across the entire codebase -- finds code by meaning, not just text matching. Use this instead of grep/glob when you need to find implementations, understand how features work, or locate related code without knowing exact names or keywords. Accepts natural language queries (e.g., 'authentication logic', 'database connection handling') or code snippets. Returns matching code chunks with file paths, line numbers, and relevance scores. Start with a small limit (e.g., 5); if most results look relevant, use offset to paginate for more.