Explicit TWT timing and shared-control executor checkpoint on ns-3.48 Local acceptance: 195 test cases, both local-execution probes and ten native-resolution mapper processes passed. Actual Setup/Accept/ACK tests cover bidirectional data, controlled response and ACK loss, MAC retries and explicit lifecycle cleanup. Scope: caller-reference TSF mapping and explicit paired installation/removal for supported ordinary individual unannounced single-link HE/QoS agreements, with version-owned compensation. Autonomous negotiated execution, automatic TSF synchronization, AP admission and duplicate recovery, protected/broadcast TWT, MLO/EMLSR, OFDMA, energy validation and full-frame containment remain unsupported. The earlier MLO regression remains unresolved; see doc/twt/REGRESSION_STATUS.md.