Lexer, recursive-descent parser (AND/OR/NOT, parentheses, implicit AND,
IN lists, size/age/date units) and an evaluator that computes filtered
subtree sizes in two linear passes without double counting.
Single-writer controller with a select loop that offers jobs and accepts
results simultaneously, so bounded channels cannot deadlock. statx/fstatat
relative to the directory fd on Linux/macOS, portable fallback elsewhere.
Hard links counted once, symlink loops detected, virtual filesystems
skipped, errors classified and surfaced.
Andy Dixon