Deep SCM stress

Application-scale Quarto stress for the representation bridge and graph-constrained deep mechanisms (Phase 1–2b). Package test/ remains the merge gate.

Quarto notebook: docs/stress/deep_scm_stress.qmd

cd docs/stress && quarto render deep_scm_stress.qmd

Estimation on codes (mediation / LMTP / missing $Y$): CausalTargeted deepscmestimation_stress.qmd.

Landing: STRESS.md.

Covers: large / wide encode, AgeSCM-pattern Lux 1D-CNN stub, ODE residual + do_pin, generative L3 (scalar and multi-dim), Phase 1→2b hand-off, NaN passthrough.

Deferred (not in this notebook or core): UniversalDiffEq hard wiring, Flux-in-CausalDynamics, non-additive image DeepSCM, full MIRS cohort files.