tests: positive regression guard — assets=-$1M passes benchmark validation

Asserts that `validate_initial_conditions` admits a subject placed at
`assets = -1_000_000` in `retiree_nomc_inelig_canwork` under the
benchmark model. Encodes the economic story: with the consumption
floor / transfer system, any past assets level is representable —
`c = c_floor` is always feasible because `transfers` tops up
cash-on-hand to the floor.

The test passes today on benchmark params; it doesn't reproduce the
gpu-01 failure (production-side, separate setup loaded by
`aca-estimation`'s `assemble_fixed_params`). Kept as a permanent
regression guard so a future change that re-introduces a constraint
shape that rejects extreme negatives is caught immediately at
benchmark scale.

Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>

Author: hmgaudecker

tests/test_initial_conditions_extreme_assets.py

@@ -0,0 +1,50 @@
+"""Subjects at extreme negative assets must clear `validate_initial_conditions`.
+
+The transfer system (`agent.assets_and_income.transfers`) tops cash-on-hand
+to `consumption_floor * equivalence_scale` at any starting state, so the
+lowest consumption-grid point is always a feasible action regardless of
+how negative starting assets are. The model's constraints — and pylcm's
+`validate_initial_conditions` pass — must reflect this.
+"""
+
+import jax.numpy as jnp
+from lcm.simulation.initial_conditions import validate_initial_conditions
+
+from aca_model.benchmark import (
+    create_benchmark_model,
+    get_benchmark_initial_conditions,
+    get_benchmark_params,
+)
+
+
+def test_extreme_negative_assets_subject_passes_validation() -> None:
+    """A subject placed at `assets = -1_000_000` clears initial-conditions validation.
+
+    HRS bottom-codes very-large-negative net wealth at exactly $-1{,}000{,}000$.
+    Such subjects should remain in the simulated population: the consumption
+    floor / transfer system absorbs them, with `c = c_floor` always feasible.
+    """
+    n_subjects = 1
+    model = create_benchmark_model(n_subjects=n_subjects)
+    _, params = get_benchmark_params(model=model)
+
+    initial_conditions = get_benchmark_initial_conditions(
+        model=model, n_subjects=n_subjects, seed=0
+    )
+    initial_conditions = {
+        **initial_conditions,
+        "assets": jnp.asarray([-1_000_000.0]),
+        "regime": jnp.asarray(
+            [model.regime_names_to_ids["retiree_nomc_inelig_canwork"]],
+            dtype=jnp.int32,
+        ),
+    }
+
+    internal_params = model._process_params(params)  # noqa: SLF001
+    validate_initial_conditions(
+        initial_conditions=initial_conditions,
+        internal_regimes=model.internal_regimes,
+        regime_names_to_ids=model.regime_names_to_ids,
+        internal_params=internal_params,
+        ages=model.ages,
+    )