A configurable lint engine for SAS source files. Walks the token stream produced by the `sas-lexer` gem and applies a set of pluggable rules covering structural defects (malformed `if` conditions, identical `then`/`else` branches, unreachable inner branches), cosmetic issues (trailing whitespace, tab expansion, line endings, encoding gremlins), and source-header conventions. Includes a `bin/sas_lint` CLI and YAML-based config.