Function build_suppression_map 

pub fn build_suppression_map(root: &GdNode, source: &str) -> SuppressionMap

Build the per-file suppression map from the parsed CST (Workstream 1 M2): each @warning_ignore("code", …) suppresses the listed codes over the single following statement/declaration, and a @warning_ignore_start("code") … @warning_ignore_restore("code") pair suppresses a region (EOF-terminated if unrestored). Unknown code names are skipped (the unknown-name meta-diagnostic is deferred — see TECH_DEBT.md).