chore: migrate server.tool() to registerTool()

Closes #14 (closed) .

server.tool() is deprecated in MCP SDK 1.29.0. Moved all 7 tools to server.registerTool(name, { description, inputSchema }, handler) — the config object folds in description + schema, handlers are unchanged. No behavior change. The large diff in advanced_search.ts is prettier reindenting the schema body one level deeper under inputSchema, not logic. Verified: lint + build clean; in-memory MCP client lists all 7 tools and ping returns pong.