Motivation

Currently, when using lang = 'rust', the tool generates flat files (e.g., code/1.two-sum.rs) in ~/.leetcode/code/. This works for LeetCode submissions but lacks a proper crate structure, causing LSP tools like rust-analyzer (in editors such as Helix, VS Code, or Neovim) to have limited features (e.g., no full autocomplete, diagnostics, or go-to-definition).