feat(kevin): KevinDecision + KevinAccountState schemas

Standalone schemas (no BaseStrategy coupling) used by both the live
signal bridge and the backtest mini-engine.

tests/shared/schemas/test_kevin.py

@@ -0,0 +1,59 @@
+"""Tests for KevinDecision + KevinAccountState pydantic schemas."""
+
+from decimal import Decimal
+
+import pytest
+from pydantic import ValidationError
+
+from shared.schemas.kevin import (
+    KevinAccountState,
+    KevinDecision,
+    KevinDecisionType,
+)
+
+
+def test_kevin_decision_open_long_requires_target_dollars():
+    d = KevinDecision(
+        decision=KevinDecisionType.OPEN_LONG,
+        symbol="NVDA",
+        target_dollars=Decimal("2000"),
+        holding_days=10,
+        effective_conviction=Decimal("0.75"),
+        rationale="conv 0.7 + 1 boost",
+    )
+    assert d.symbol == "NVDA"
+    assert d.target_dollars == Decimal("2000")
+
+
+def test_kevin_decision_close_long_does_not_require_target_dollars():
+    d = KevinDecision(
+        decision=KevinDecisionType.CLOSE_LONG,
+        symbol="NVDA",
+        rationale="kevin reverse",
+    )
+    assert d.target_dollars is None
+
+
+def test_kevin_decision_open_long_rejects_missing_target_dollars():
+    with pytest.raises(ValidationError, match="target_dollars"):
+        KevinDecision(
+            decision=KevinDecisionType.OPEN_LONG,
+            symbol="NVDA",
+            rationale="missing $",
+        )
+
+
+def test_kevin_account_state_held_symbols_lookup():
+    state = KevinAccountState(
+        equity_usd=Decimal("100000"),
+        cash_usd=Decimal("80000"),
+        held_positions={"NVDA": Decimal("5000"), "INTC": Decimal("2000")},
+        blocklisted_symbols={"WMT"},
+        daily_trade_count=2,
+        daily_alloc_usd=Decimal("4000"),
+        paused=False,
+    )
+    assert state.is_held("NVDA")
+    assert not state.is_held("AAPL")
+    assert state.is_blocklisted("WMT")
+    assert not state.is_blocklisted("NVDA")