Per spec §6.7. The walk-forward generator emits `test_start..test_end`
per fold but the trainer at `mod.rs:1294` only consumed train+val — the
12.5% test slice was silently dropped, the model was never measured on
held-out data the train/val pipeline didn't see.
This commit lands the foundation: `set_test_data_from_slices` stashes
the per-fold range immediately after `set_val_data_from_slices`, gated
on `fold.test_end > fold.test_start` for defensively-empty slices. A
`set_test_data_observer` hook lets unit tests verify the wiring without
spinning up a full GPU eval pipeline.
The actual `evaluate_dqn_graphed` invocation against the stashed slice
plus the per-fold `HEALTH_DIAG test_slice fold=K test_sharpe_net=...`
emit is deferred to a follow-up commit per `feedback_no_partial_refactor`.
Wiring it through requires either standing up a second
`GpuBacktestEvaluator` instance (parallel to the val one at
`metrics.rs:550`) or refactoring the existing val evaluator to swap
window data between val and test eval — the val evaluator's lazy-init
path is fundamentally tied to the window passed at construction. Plus
TLOB weight sync, ISV signal wiring, and a `training_mode` toggle (no
such field exists yet on `DQNTrainer`).
This deferral matches the Phase 1.5 (kernel + launcher first, trunk
consumer follow-up) and Phase 1.6 (stash dev/holdout slices, eval
consumer follow-up) precedents on this branch. The stash + observer
surface is the analogous foundation; the L40S smoke once Task 1.7.b
lands will surface the per-fold `test_sharpe_net` HEALTH_DIAG line as
the canonical end-to-end verifier.
New oracle test `set_test_data_from_slices_fires_observer_and_stashes`
in `sp15_phase1_oracle_tests.rs` constructs a real trainer (sync init,
no GPU forward), registers an observer, exercises the API with a
synthetic [5000..6000) range, asserts the observer fires once with the
right bounds. Passes locally on RTX 3050 Ti.
`docs/dqn-wire-up-audit.md` extended with a Phase 1.7 entry documenting
what landed, what's deferred, the wire-up locations, and the rationale.
Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>
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