//! SPG SQL front-end. v0.2 ships only the lexer + a minimal recursive-descent
//! parser for the `SELECT [..] FROM [..] WHERE [..]` subset.
//!
//! Layers (each in its own module):
//!
//! - [`lexer`] — byte stream → tokens
//! - [`ast`] — abstract syntax tree types + `Display` (pretty-print)
//! - [`parser`] — tokens → AST (Pratt parser for expression precedence)
extern crate alloc;