…s baked in

`scripts/dispatch-distill-stage-d.sh` is the operator entrypoint for
Phase 4 Stage D production training. Captures the PMAT-701 cascade
post-mortem lessons in a single dispatchable wrapper:

* **cuBLAS default** (PMAT-704 / #1879). `APR_DISTILL_TEACHER_BACKEND=auto`
  by default; operators can opt into the slower memory-constrained
  Realizar path via `APR_DISTILL_TEACHER_BACKEND=realizar-q4k`.
* **Per-step monitoring** (PMAT-705 / #1881). `APR_DISTILL_LOG_EVERY=50`
  default — visible loss progress without log spam. Operators can set
  =1 for verbose mode or =0 to silence.
* **PMAT-699 P0 checkpointing** every 5000 steps (durability — survives
  kill / crash).
* **PMAT-703 vocab alignment** auto-applies inside the cuda backend
  when teacher.vocab > student.vocab (no operator config needed).
* **Disk preflight**: requires ≥ 15 GB free on /home/noah (Stage D 50K
  writes ~12 GB of checkpoints; PMAT-704 cascade post-mortem caught
  gx10 at 98 % full). Fails fast with cleanup candidates listed.
* **Teacher / student validation**: requires stamped APR metadata
  (apr-leaderboard checkpoint by default — the dispatch-script's
  `apr import --preserve-q4k` path fails the cuda backend's
  metadata-required check, surfaced by PMAT-704 incident).
* **Process-alive check**: 10 s post-dispatch verification catches
  early validation errors so the operator doesn't walk away from a
  failed dispatch.

The wrapper is intentionally separate from `dispatch-distill-phase-3-gx10.sh`
which remains the Phase 3 smoke entrypoint. Stage D is production scope
and shouldn't inherit smoke defaults (see SPEC-DISTILL-001 §86 +
memory `feedback_smoke_defaults_leak_into_production.md`).

## Override env vars

* `STEPS` (default 50000)
* `BATCH_SIZE` (default 32)
* `LR` (default 1.5e-5)
* `T` (default 4.0)
* `ALPHA` (default 0.3)
* `DATASET_DIR` (unset → synthetic; set to a `.bin` shard dir for real corpus)
* `APR_DISTILL_LOG_EVERY` (default 50)
* `APR_DISTILL_CHECKPOINT_EVERY` (default 5000)
* `APR_DISTILL_TEACHER_BACKEND` (default `auto`)
* `DISK_FREE_REQUIRED_GB` (default 15)
* `DRY_RUN=1` to plan only

## QA

* `bash -n scripts/dispatch-distill-stage-d.sh` — syntax-ok
* `bashrs lint scripts/dispatch-distill-stage-d.sh` — 0 errors
  (warnings are df-non-determinism + path-traversal-ln, both expected
  for an operator-supplied path dispatcher)

Co-Authored-By: Claude Opus 4.7 <noreply@anthropic.com>