Function extractExtensions

src/project-config.ts:167–186

* Validate the `extensions` map. Every failure mode degrades to "no overrides * from this entry" — a bad value or a typo'd language never throws.

(parsed: object, file: string)

 * from this entry" — a bad value or a typo'd language never throws.
 */
function extractExtensions(parsed: object, file: string): Record<string, Language> {
  const exts = (parsed as ProjectConfig).extensions;
  if (!exts || typeof exts !== 'object' || Array.isArray(exts)) return EMPTY_EXTENSIONS;

  const out: Record<string, Language> = {};
  for (const [rawKey, rawVal] of Object.entries(exts)) {
    const key = normalizeExtKey(rawKey);
    if (!key) {
      logWarn(`Ignoring extension mapping in ${PROJECT_CONFIG_FILENAME}: "${rawKey}" is not a valid file extension`, { file });
      continue;
    }
    if (typeof rawVal !== 'string' || !isLanguageSupported(rawVal as Language)) {
      logWarn(`Ignoring extension "${rawKey}" in ${PROJECT_CONFIG_FILENAME}: "${String(rawVal)}" is not a supported language`, { file });
      continue;
    }
    out[key] = rawVal as Language;
  }

  return Object.keys(out).length > 0 ? out : EMPTY_EXTENSIONS;
}

/**
 * Validate the `includeIgnored` patterns: an array of non-empty gitignore-style