Merge nucleic/sleek-ember-seal-uady into dev

README.md

@@ -554,6 +554,34 @@ distillation regression cannot overwrite the 80.31% candidate. Teacher agreement
 reported for diagnosis but does not enter deep checkpoint selection; overall and hard
 primary label accuracy remain the only selection inputs.
 
+### Pause and resume purpose-deep training
+
+`train_deep_mlx.py` handles both `Ctrl-C` (`SIGINT`) and `SIGTERM` gracefully. Press
+`Ctrl-C` once: the current optimizer step finishes, then the trainer atomically saves the
+current model, AdamW state and learning-rate cursor, epoch and next batch, exact shuffle
+order, accumulated losses, RNG state, best-selection state, and history under
+`<output-dir>/resume/`. It exits with the conventional signal-derived status only after
+that checkpoint is durable. A second `Ctrl-C` forces an immediate interruption.
+
+The pause message prints the complete resume command. For the distilled run above it is:
+
+```bash
+ml/purpose-classifier/venv/bin/python -u \
+  ml/purpose-classifier/train_deep_mlx.py \
+  --resume-training \
+    ml/purpose-classifier/outputs/purpose-deep-v1-base-mlx-distilled/resume
+```
+
+`--resume-training` is sufficient by itself: it restores the original dataset,
+distillation, schedule, loss, and selection arguments from the checkpoint. It also verifies
+hashes of the training split, validation split, and teacher cache before loading. The
+checkpoint resumes at the next unprocessed batch—even if stopped after the last training
+batch but before epoch evaluation. Normal completion removes the large optimizer resume
+artifact while retaining the selected `model/` and reports.
+
+This applies to processes started with the updated script. A process already running older
+code cannot acquire signal handling retroactively.
+
 The historical large-rung rule required base to qualify first, large to beat base by at
 least two hard-slice points, and deep to reach 97% scored overall while beating lite by
 five hard-slice points. Neither the v1 nor Sol-high v2 base result unlocked that rung.