malkhut(spec): item 4 — ScenarioLibrary sweep for Mode 1 coverage

ScenarioLibrary sweeps the state space (not samples) across:
  - spread_mult: [0.1, 0.5, 1.0, 2.0, 5.0, 10.0]
  - depth_fraction: [0.01, 0.05, 0.1, 0.3, 0.5, 1.0]
  - toxicity: [0.0, 0.3, 0.7, 1.0]
  - regime: [normal, crisis, recovery, transition]

Default: 13 assets × 576 grid points = 7,488 scenarios.
Customizable: specify symbols, dimensions, ranges.

7 tests covering: grid size, sweep output, point fields,
regime coverage, custom dimensions, summary, factory function.

MALKHUT/malkhut/tests/test_scenario_library.py

@@ -0,0 +1,56 @@
+"""
+Tests for ScenarioLibrary — sweep coverage.
+"""
+import pytest
+from malkhut.training.scenario_library import ScenarioLibrary, SweepPoint, get_scenario_library
+
+
+class TestScenarioLibrary:
+    def test_default_grid_size(self):
+        lib = ScenarioLibrary()
+        size = lib.grid_size()
+        assert size == 13 * 6 * 6 * 4 * 4  # 13 assets × 576 grid points
+        print(f'  Default grid: {size} points')
+
+    def test_sweep_produces_points(self):
+        lib = ScenarioLibrary(symbols=("BTCUSDT",))
+        points = lib.sweep()
+        assert len(points) == 6 * 6 * 4 * 4  # 576 for one asset
+
+    def test_sweep_point_fields(self):
+        lib = ScenarioLibrary(symbols=("BTCUSDT",))
+        points = lib.sweep()
+        p = points[0]
+        assert isinstance(p, SweepPoint)
+        assert p.symbol == "BTCUSDT"
+        assert isinstance(p.spread_mult, float)
+        assert isinstance(p.depth_fraction, float)
+        assert isinstance(p.toxicity, float)
+        assert isinstance(p.regime, str)
+        assert isinstance(p.label, str)
+
+    def test_sweep_covers_all_regimes(self):
+        lib = ScenarioLibrary(symbols=("BTCUSDT",))
+        points = lib.sweep()
+        regimes = set(p.regime for p in points)
+        assert regimes == {"normal", "crisis", "recovery", "transition"}
+
+    def test_custom_dimensions(self):
+        lib = ScenarioLibrary(
+            symbols=("BTCUSDT", "ETHUSDT"),
+            spread_mults=[1.0, 5.0],
+            depth_fracs=[0.1, 0.5],
+            tox_levels=[0.0, 0.5],
+            regimes=["normal", "crisis"],
+        )
+        assert lib.grid_size() == 2 * 2 * 2 * 2 * 2  # 32 points
+
+    def test_summary(self):
+        lib = ScenarioLibrary()
+        s = lib.summary()
+        assert "13" in s
+        assert "7488" in s  # 13 × 576
+
+    def test_get_scenario_library(self):
+        lib = get_scenario_library()
+        assert lib.grid_size() > 0