ADR-0027 rev7 (Megatron TP + worker-wait generalization) + ADR-0026 typo fix

ADR-0027 is a design-only change (no production code). Rev 7 closes design
across 7 iterations of review. Key decisions:

- D0 (worker-wait generalization): ctx.wait in worker context yields to
  main scheduler, which drains env.run. Solves ADR-0024 Phase B orphan
  bug (ring_default_ws strict xfail). Normative contracts on resume
  invariant, fast-path, main-context non-reentrance, barrier
  loop-until-empty, and scheduler non-progress as user contract.
- D0.5 (host-read barrier): Tensor.numpy/data/__getitem__/__repr__/copy_
  auto-drain pending before reading. Closed-set via explicit registry
  (T5.g). copy_ uses global-pending barrier with explicit
  over-serialization tradeoff.
- D1 (torch.multiprocessing.spawn): real-PyTorch API-signature parity,
  cooperative greenlet scheduler internally. Explicit non-goal on
  process isolation / address space / failure isolation. Sibling
  cleanup via SystemExit + SpawnException(errors) wrapping root-cause
  ranks.
- D4/D5 (TP layers): ColumnParallelLinear / RowParallelLinear use
  torch.launch(gemm_kernel) — no host-side torch.matmul. Yield-safety
  contract normatively required for all TP forward paths.
- Supersedes ADR-0024 D7/D12/D13 as design (none landed). Source of
  truth declared normative.

Test strategy: T1-T8 with numerical-correctness primary (not mean/
aggregate-only), orphan invariant direct assertion, host-read barrier
closed-set via registry. Phase 2 acceptance = 524 passed + 0 xfail
(ring_default_ws unblocked by D0).

ADR-0026 typo fix: torch.cuda.set_device → torch.ahbm.set_device in
DPPolicy docstring (ADR-0024 D10 convention).

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

docs/adr/ADR-0026-dppolicy-intra-device.md

@@ -69,9 +69,9 @@ class DPPolicy:
 class DPPolicy:
     """Intra-device (cube × PE) data-parallel policy.
 
-    SIP-level placement is controlled by ``torch.cuda.set_device(rank)``
+    SIP-level placement is controlled by ``torch.ahbm.set_device(rank)``
-    (ADR-0024) and, for model-level TP, by Megatron-style parallel layers
+    (ADR-0024 D10) and, for model-level TP, by Megatron-style parallel
-    (ADR-0027). DPPolicy does not cross SIP boundaries.
+    layers (ADR-0027). DPPolicy does not cross SIP boundaries.
     """
     cube: Literal["replicate", "column_wise", "row_wise"] = "replicate"
     pe: Literal["replicate", "column_wise", "row_wise"] = "replicate"