Fix USB radio stalls and add durable replay timestamp recovery

test/fixtures/regular_file_reads/InternalFileSystem.h

@@ -0,0 +1,6 @@
+#pragma once
+
+// The production helper only needs a valid owner for a closed LittleFS file.
+// The harness defines this object without any filesystem or hardware access.
+struct FakeFS;
+extern FakeFS InternalFS;