chore(8.0): final pre-RC1 sweep — API consistency, named errors, orphans, zero-cast codebase

src/utils/mutex.ts

@@ -278,6 +278,8 @@ export function getGlobalMutex(): MutexInterface {
  */
 export async function cleanupMutexes(): Promise<void> {
   if (globalMutex && 'cleanup' in globalMutex) {
-    await (globalMutex as any).cleanup()
+    // Only FileMutex (defined above) carries a cleanup() method; the 'in'
+    // check above guarantees we hold that implementation.
+    await (globalMutex as FileMutex).cleanup()
   }
 }