feat: DailyScorecard model for per-market performance review (issue #90)

- Add DailyScorecard dataclass with market-scoped fields
- Fields: date, market, decisions, pnl, win_rate, scenario_match_rate, lessons, cross_market_note
- Export from src/evolution/__init__.py

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

src/evolution/scorecard.py

@@ -0,0 +1,25 @@
+"""Daily scorecard model for end-of-day performance review."""
+
+from __future__ import annotations
+
+from dataclasses import dataclass, field
+
+
+@dataclass
+class DailyScorecard:
+    """Structured daily performance snapshot for a single market."""
+
+    date: str
+    market: str
+    total_decisions: int
+    buys: int
+    sells: int
+    holds: int
+    total_pnl: float
+    win_rate: float
+    avg_confidence: float
+    scenario_match_rate: float
+    top_winners: list[str] = field(default_factory=list)
+    top_losers: list[str] = field(default_factory=list)
+    lessons: list[str] = field(default_factory=list)
+    cross_market_note: str = ""