Function normalize_schema_pattern_dialects 

pub fn normalize_schema_pattern_dialects(schema: &mut Value)

Normalize regex dialects in every schema-position pattern keyword and patternProperties key. Provider schemas carry Go/RE2 spellings — notably a leading global (?i) — that Draft-07’s ECMA-262 dialect rejects; conforming validators refuse the whole schema over one such pattern. Runs once at provider-fragment ingestion, the boundary where foreign dialect text enters the system, so every downstream consumer sees portable spellings. Rewrites are language-exact (a case fold, never a widening), so an untranslatable pattern stays as-is for the fixture hygiene gate to report rather than silently changing what the schema accepts.