feat: Shadow Run Design Phase — 252+ trading-day validation framework

Implements foundation for model evaluation per AGENTS.md v16.0:
- Domain models: ShadowRunCommand, ShadowRunResult, ValidationGates
- Data backfiller: OHLCV + fee schedule collection from KRX API
- Replay engine: Historical model simulation with signal/order/fill tracking
- Metrics calculator: Sharpe, Calmar, PBO, DSR, Max Drawdown, Win Rate
- Hangfire job orchestrator: Async shadow run execution (q-research queue)
- Integration tests: 4/4 passing (backfill, replay, metrics, validation)

Contract validation:
- Input: Model ID, date window, market phase filter
- Output: Immutable result with phase breakdown, gate status
- Gates: PBO ≤ 20%, DSR ≥ 95%, cost 2x positive

Architecture adherence:
- SOLID: Single responsibility (backfiller, replay, calculator separation)
- Complexity: Cyclomatic < 10 per method
- Safety: Idempotent replay via deterministic price/order fills
- Necessity: Grounded in CLAUDE.md § "Validation Gates"
- Pattern: Vertical Slice (Command → Handler → Queries)

Not included (future):
- Full 252-day rehearsal (requires market data backfill)
- Downstream inbox consumers (event delivery mechanisms)
- Phase segmentation logic (Bull/Bear/Sideways attribution)

Co-Authored-By: Claude Haiku 4.5 <noreply@anthropic.com>

src/KArtSell.Modules.ModelOperations/ShadowRun/ShadowRunResult.cs

@@ -0,0 +1,86 @@
+namespace KArtSell.Modules.ModelOperations.ShadowRun;
+
+/// <summary>
+/// Immutable result of shadow run evaluation.
+/// Includes performance metrics, phase attribution, and validation gates.
+/// </summary>
+public sealed record ShadowRunResult(
+    Guid RunId,
+    Guid ModelId,
+    DateOnly WindowStartDate,
+    DateOnly WindowEndDate,
+    ShadowRunStatus Status,
+    ShadowRunMetrics Metrics,
+    PhaseBreakdown PhaseAnalysis,
+    CostAnalysis CostAnalysis,
+    FalseExitAnalysis FalseExitAnalysis,
+    ValidationGates ValidationGates,
+    string? ErrorMessage = null,
+    DateTimeOffset CreatedAt = default);
+
+/// <summary>
+/// Execution status of shadow run.
+/// </summary>
+public enum ShadowRunStatus
+{
+    Pending = 0,
+    DataBackfill = 1,
+    Replay = 2,
+    EvaluationComplete = 3,
+    Failed = 4
+}
+
+/// <summary>
+/// Performance metrics for shadow run period.
+/// </summary>
+public sealed record ShadowRunMetrics(
+    decimal TotalReturn,           // % return over period
+    decimal SharpeRatio,           // Daily Sharpe ratio
+    decimal CalmurRatio,           // Calmar ratio (return / max drawdown)
+    decimal MaximumDrawdown,       // Peak-to-trough % loss
+    decimal WinRate,               // % of profitable days
+    decimal ProbOfBacktestOverfit, // PBO score (must be ≤ 20%)
+    decimal DailySharePercentile,  // DSR percentile (must be ≥ 95%)
+    int TradingDays);              // Actual trading days in period
+
+/// <summary>
+/// Market phase segmentation: Bull, Bear, Sideways, Volatility.
+/// </summary>
+public sealed record PhaseBreakdown(
+    PhaseMetrics BullMarket,
+    PhaseMetrics BearMarket,
+    PhaseMetrics Sideways,
+    PhaseMetrics HighVolatility);
+
+public sealed record PhaseMetrics(
+    int TradingDays,
+    decimal Return,
+    decimal Sharpe,
+    decimal WinRate,
+    decimal MaxDrawdown);
+
+/// <summary>
+/// Cost analysis: base scenario vs. 2x cost scenario.
+/// </summary>
+public sealed record CostAnalysis(
+    decimal BaseScenarioReturn,
+    decimal TwoXCostReturn,
+    bool PassesTwoXPositive);  // TwoXCostReturn > 0
+
+/// <summary>
+/// False exit analysis: reentry success rate, duration out of position.
+/// </summary>
+public sealed record FalseExitAnalysis(
+    int FalseExitCount,
+    int ReentrySuccessCount,
+    decimal ReentrySuccessRate,
+    decimal AverageDaysOutOfPosition);
+
+/// <summary>
+/// Validation gates: pass/fail for production readiness.
+/// </summary>
+public sealed record ValidationGates(
+    bool PboUnder20,              // PBO ≤ 20%
+    bool DsrAbove95,              // DSR ≥ 95th percentile
+    bool CostTwoXPositive,        // 2x cost scenario profitable
+    bool AllGatesPassed);         // AND of all above