A roof capped below two panels is still offered no PV 🟩

Pins the ADR-0058 install floor delivered with the tracer slice (rung_max
< 2 returns empty) — no red phase.

Co-Authored-By: Claude Fable 5 <noreply@anthropic.com>

tests/domain/modelling/test_solar_config_selection.py

@@ -348,3 +348,28 @@ def test_sub_ladder_rungs_never_take_from_north_planes() -> None:
     assert [c.panels_count for c in configs] == [2, 3]
     assert [c.yearly_energy_dc_kwh for c in configs] == [639.0, 958.5]
     assert all(s.azimuth_degrees == 180.0 for c in configs for s in c.segments)
+
+
+def test_roof_capped_below_two_panels_still_yields_no_configs() -> None:
+    # ADR-0058 — the install floor: a roof whose cap resolves below 2 panels
+    # is never offered PV. Max 2 → cap 1.4 < 2; the ladder cliff is the
+    # correct outcome here, not a Sub-Ladder rung.
+
+    # Arrange
+    potential = SolarPotential(
+        panel_capacity_watts=400.0,
+        max_array_panels_count=2,
+        configurations=(
+            SolarPanelConfiguration(
+                panels_count=2,
+                yearly_energy_dc_kwh=640.0,
+                segments=(_segment(2, 180.0, 640.0),),
+            ),
+        ),
+    )
+
+    # Act
+    configs = select_conservative_configs(potential)
+
+    # Assert
+    assert configs == ()