feat: model validation, calibration, and signal quality layer

- Migration 035: prediction_snapshots, prediction_outcomes, signal_evidence_links, model_metric_snapshots tables + SQL views
- Prediction snapshot writer with canonical evidence keys, duplicate detection, contribution scores
- Outcome evaluator across 5 horizons (1h, 6h, 1d, 7d, 30d)
- Metrics engine: ECE, Brier score, IC, Rank IC, benchmark comparison
- Attribution engine: per-source, per-catalyst, per-layer performance
- Calibration engine: Bayesian shrinkage source reliability
- Quality gate for live trading eligibility with configurable thresholds
- 7 new /api/validation/* endpoints
- Upgraded OpsModel dashboard with validation tab
- Enhanced recommendation display with calibration context
- Backtest replay validation mode
- 86 Python tests (unit + property-based), 179 frontend tests passing

services/aggregation/worker.py

@@ -64,6 +64,7 @@ from services.shared.metrics import (
     AGGREGATION_WINDOWS_COMPUTED,
 )
 from services.shared.schemas import TrendDirection, TrendSummary, TrendWindow
+from services.trading.model_quality_gate import QualityGateResult, evaluate_quality_gate
 
 logger = logging.getLogger(__name__)
 
@@ -1576,10 +1577,34 @@ async def aggregate_company(
     # Mid-cycle changes take effect on the next cycle.
     probabilistic = await fetch_probabilistic_scoring_enabled(pool)
     pipeline_mode = "probabilistic" if probabilistic else "heuristic"
+
+    # --- Quality gate evaluation (Req 11.2, 11.3) ---
+    # Evaluate model quality gate at the start of each aggregation cycle.
+    # When the gate fails, all recommendations are forced to paper mode.
+    # Gate evaluation failure defaults to paper-only (fail-safe).
+    quality_gate_passed = False
+    try:
+        gate_result: QualityGateResult = await evaluate_quality_gate(pool)
+        quality_gate_passed = gate_result.passed
+        logger.info(
+            "Quality gate for %s cycle: %s — %s",
+            ticker,
+            "PASS" if gate_result.passed else "FAIL",
+            gate_result.reason,
+        )
+    except Exception:
+        logger.exception(
+            "Quality gate evaluation failed for %s cycle — "
+            "defaulting to paper-only mode (fail-safe)",
+            ticker,
+        )
+        quality_gate_passed = False
+
     logger.info(
-        "Aggregation cycle for %s: pipeline_mode=%s",
+        "Aggregation cycle for %s: pipeline_mode=%s quality_gate=%s",
         ticker,
         pipeline_mode,
+        "passed" if quality_gate_passed else "failed",
     )
 
     # --- Regime detection (Req 7.1, 7.2, 7.3, 7.8, 7.9) ---
@@ -1647,6 +1672,20 @@ async def aggregate_company(
             ticker_returns=ticker_returns,
             ticker_volumes=ticker_volumes,
         )
+
+        # When quality gate fails, annotate the trend summary so the
+        # recommendation engine forces paper mode (Req 11.2, 11.3).
+        if not quality_gate_passed:
+            ctx = summary.market_context
+            if isinstance(ctx, dict):
+                ctx["quality_gate_passed"] = False
+            elif ctx is not None and hasattr(ctx, "model_dump"):
+                ctx_dict = ctx.model_dump()
+                ctx_dict["quality_gate_passed"] = False
+                summary.market_context = ctx_dict
+            else:
+                summary.market_context = {"quality_gate_passed": False}
+
         summaries.append(summary)
 
     return summaries