feat: signal math upgrade — probabilistic, regime-aware scoring pipeline

Implement full probabilistic signal processing pipeline gated behind
probabilistic_scoring_enabled feature flag in risk_configs:

- Bayesian log-likelihood accumulator with Beta posterior and entropy
- Regime detector (trend-following, panic, mean-reversion, uncertainty)
- Source accuracy tracker with per-source historical prediction accuracy
- Sigmoid confidence gate replacing binary gate
- Information gain surprise weighting for rare events
- Adaptive recency decay with event-specific half-lives
- Regime multiplier replacing market context multiplier
- Weighted disagreement entropy for contradiction detection
- Multiplicative macro exposure with conditional integration
- Graph-distance attenuated competitive signal propagation
- Exponentially weighted momentum with volatility scaling
- Expected value recommendation gate

All changes backward-compatible: flag=false preserves exact current behavior.
New outputs stored in existing JSONB columns (no schema changes except
source_accuracy table via migration 034).

Tests: 26 property-based tests (14 correctness properties), 99 unit tests,
1789 total tests passing with zero regressions.

services/shared/schemas.py

@@ -224,6 +224,15 @@ class TrendSummary(BaseModel):
     market_context: Optional[MarketContext] = None
     generated_at: datetime = Field(default_factory=lambda: datetime.now(tz=timezone.utc))
 
+    # New optional fields for probabilistic mode
+    p_bull: Optional[float] = None              # Bayesian bullish probability
+    alpha: Optional[float] = None               # Beta posterior α
+    beta_param: Optional[float] = None          # Beta posterior β (named to avoid shadowing)
+    bayesian_confidence: Optional[float] = None  # 1 - 4αβ/(α+β)²
+    entropy: Optional[float] = None             # Shannon entropy H
+    regime: Optional[str] = None                # Market regime classification
+    pipeline_mode: str = "heuristic"            # "heuristic" or "probabilistic"
+
 
 # --- Recommendation ---
 
@@ -246,6 +255,11 @@ class Recommendation(BaseModel):
     model_metadata: ModelMetadata = Field(default_factory=ModelMetadata)
     generated_at: datetime = Field(default_factory=lambda: datetime.now(tz=timezone.utc))
 
+    # New optional fields for probabilistic mode
+    expected_value: Optional[float] = None      # EV = P_bull·R_up - P_bear·R_down
+    p_bull: Optional[float] = None              # Bayesian bullish probability used
+    pipeline_mode: str = "heuristic"            # "heuristic" or "probabilistic"
+
 
 # --- Global News Interpolation ---