Function normalizeExtKey

src/project-config.ts:95–104

* Normalize a user-provided extension key to the `.ext` lowercase form used by * the built-in map. Returns null for keys that can never match a real file * extension (so the caller warns and skips): * - empty / just "." * - multi-part (".d.ts") — language detection keys off the FINAL extensi

(raw: string)

 *   - anything containing a path separator.
 */
function normalizeExtKey(raw: string): string | null {
  if (typeof raw !== 'string') return null;
  let ext = raw.trim().toLowerCase();
  if (!ext) return null;
  if (!ext.startsWith('.')) ext = '.' + ext;
  const body = ext.slice(1);
  if (!body) return null;
  if (body.includes('.') || body.includes('/') || body.includes('\\')) return null;
  return ext;
}

/**
 * Read + JSON-parse a `codegraph.json` once and return its validated view.