feat(ga): fitness v0 (DSR - dd_penalty * max_dd, kill on adversarial high)

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

tests/unit/test_fitness.py

@@ -0,0 +1,45 @@
+from multi_swarm.agents.adversarial import AdversarialReport, Finding, Severity
+from multi_swarm.agents.falsification import FalsificationReport
+from multi_swarm.ga.fitness import compute_fitness
+
+
+def make_falsification(
+    dsr: float = 0.7, max_dd: float = 0.2, n_trades: int = 30
+) -> FalsificationReport:
+    return FalsificationReport(
+        sharpe=1.5,
+        dsr=dsr,
+        dsr_pvalue=0.05,
+        max_drawdown=max_dd,
+        total_return=0.3,
+        n_trades=n_trades,
+        n_bars=500,
+    )
+
+
+def test_fitness_zero_trades_is_zero() -> None:
+    f = make_falsification(n_trades=0)
+    a = AdversarialReport()
+    assert compute_fitness(f, a) == 0.0
+
+
+def test_fitness_increases_with_dsr() -> None:
+    a = AdversarialReport()
+    f1 = make_falsification(dsr=0.5)
+    f2 = make_falsification(dsr=0.9)
+    assert compute_fitness(f2, a) > compute_fitness(f1, a)
+
+
+def test_fitness_decreases_with_drawdown() -> None:
+    a = AdversarialReport()
+    f1 = make_falsification(max_dd=0.1)
+    f2 = make_falsification(max_dd=0.4)
+    assert compute_fitness(f1, a) > compute_fitness(f2, a)
+
+
+def test_fitness_zeroed_by_high_severity_finding() -> None:
+    f = make_falsification()
+    a = AdversarialReport(
+        findings=[Finding(name="degenerate", severity=Severity.HIGH, detail="x")]
+    )
+    assert compute_fitness(f, a) == 0.0