mix_fingerprint: fold the manifest's per-shard sha256 into the corpus identity (names+sizes could collide across rebuilds); phase4_session repins shard_dataset

kernels/phase4_session.py

@@ -140,7 +140,7 @@ def main():
         "ounce100m_credentials.py": ("ounce100m_credentials.py",
                                      "6525f62f03f2d73650a1eb4f70fcb52d1194caad4ca88b2d8bd8fd54f88339b6"),
         "shard_dataset.py": ("train/shard_dataset.py",
-                             "4111832e79445fb0ffce6a73a02da4c97255d6c7886762682e04a417f2695a78"),
+                             "adbcd96fbab9505a5e8dec4d2e83d00366a73f702786bffbde430195cf6f0471"),
         "hubckpt.py": ("train/hubckpt.py",
                        "c8c958417dc48db92f8be5c4b505581c746be9cc10110a358230ac47c480d5bf"),
         "train_ounce100m.py": ("train/train_ounce100m.py",