MIME type detection and extractor routing in core/mime.rs and core/extractor/bytes.rs — the extension→EXT_TO_MIME→validate→registry→extractor flow, key detection functions, the 118+ case-insensitive extension map, priority-based registry selection, wildcard MIME families, and how to add a new MIME type. Load when adding a format, wiring an extractor to a MIME type, or debugging why a file routes to the wrong (or no) extractor.