feat(phase6): per-feature signal attribution in log-odds space

Adds feat_fg_lo / feat_mom_lo / feat_news_lo / feat_mfld_lo / feat_btc_dom_lo
to every trade, all normalized to log-odds contribution for direct comparability.

- fg / mom / btc_dom: raw probability-delta × 2 → log-odds
- news / mfld: already log-odds (LOGODDS_WEIGHT already applied), no scaling
- btc_dom tracked separately in bayesian.py instead of bundled in total_adj
- reasoning string updated to fg_lo= / mom_lo= notation for self-documentation

Schema: 5 new DOUBLE PRECISION columns + 2 partial indexes
Stack: TradingSignal → Order → Trade → save_trade all carry feat fields
Startup: backfill_feature_columns() recovers fg/mom/news/mfld from old
  reasoning strings (×2 applied to fg/mom); btc_dom_lo stays NULL for legacy
API: /api/metrics/features — triggered/material split per feature with
  two-level thresholds (0.05 for fg/mom/btc_dom, 0.10 for news/mfld)
API: /api/trades/legacy — exposes pre-Phase-1 trades (edge_net IS NULL)
API: _enrich_trade backward-compat: reads DB columns first, falls back to
  reasoning regex with unit conversion for pre-Phase-6 trades

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

bot/strategy/bayesian.py

@@ -160,6 +160,16 @@ class TradingSignal:
     family_key: str = ""
     # ── Phase 4: regime ──────────────────────────────────────────────────────
     regime_min_edge: float = 0.10
+    # ── Phase 6: per-feature log-odds contributions ───────────────────────────
+    # All values are in log-odds space for direct comparability.
+    # feat_fg_lo / feat_mom_lo: probability-delta × 2 → log-odds.
+    # feat_news_lo / feat_mfld_lo: already log-odds (no scaling).
+    # feat_btc_dom_lo: btc-dominance probability-delta × 2 → log-odds.
+    feat_fg_lo:      float = 0.0
+    feat_mom_lo:     float = 0.0
+    feat_news_lo:    float = 0.0
+    feat_mfld_lo:    float = 0.0
+    feat_btc_dom_lo: float = 0.0
 
 
 class BayesianStrategy:
@@ -379,11 +389,14 @@ class BayesianStrategy:
         adjustments.append(_fg_contribution)
 
         # Signal 3: BTC dominance — hurts altcoins when high
+        _btc_dom_contribution = 0.0
         if (is_eth or is_altcoin or is_general_crypto) and ext.btc_dominance > 55:
-            adjustments.append(-0.03 if is_price_above else 0.03)
+            _btc_dom_contribution = -0.03 if is_price_above else 0.03
+            adjustments.append(_btc_dom_contribution)
             sources.append(f"BTC dom: {ext.btc_dominance:.1f}% (high → alt pressure)")
         elif (is_eth or is_altcoin or is_general_crypto) and ext.btc_dominance < 45:
-            adjustments.append(0.03 if is_price_above else -0.03)
+            _btc_dom_contribution = 0.03 if is_price_above else -0.03
+            adjustments.append(_btc_dom_contribution)
             sources.append(f"BTC dom: {ext.btc_dominance:.1f}% (low → alt season)")
 
         # Signal 4: GNews sentiment (politics only, budget-gated)
@@ -448,12 +461,19 @@ class BayesianStrategy:
         if manifold_log_adj != 0.0:
             confidence = min(confidence_cap, confidence + 0.08)
 
-        # Per-feature contribution string for audit logging
+        # Per-feature log-odds contributions (Phase 6).
+        # fg / mom / btc_dom: probability-delta × 2 → log-odds.
+        # news / mfld: already log-odds (LOGODDS_WEIGHT already applied).
+        feat_fg_lo      = _fg_contribution * 2
+        feat_mom_lo     = _momentum_contribution * 2
+        feat_news_lo    = news_log_adj
+        feat_mfld_lo    = manifold_log_adj
+        feat_btc_dom_lo = _btc_dom_contribution * 2
+
         feat_str = (
-            f"fg={_fg_contribution:+.3f} "
-            f"mom={_momentum_contribution:+.3f} "
-            f"mfld={manifold_log_adj:+.4f} "
-            f"news={news_log_adj:+.4f}"
+            f"fg_lo={feat_fg_lo:+.4f} mom_lo={feat_mom_lo:+.4f} "
+            f"news_lo={feat_news_lo:+.4f} mfld_lo={feat_mfld_lo:+.4f} "
+            f"btc_dom_lo={feat_btc_dom_lo:+.4f}"
         )
 
         # ── Phase 5: structured audit log ────────────────────────────────────
@@ -496,8 +516,7 @@ class BayesianStrategy:
             f"regime_min={regime_min:.2f} | days={days} | "
             f"family={family} | "
             f"Direction={direction} | "
-            f"fg={_fg_contribution:+.4f} mom={_momentum_contribution:+.4f} "
-            f"news={news_log_adj:+.4f} mfld={manifold_log_adj:+.4f} | "
+            f"{feat_str} | "
             f"Signals: {', '.join(sources[1:])}"
         )
 
@@ -535,6 +554,12 @@ class BayesianStrategy:
             family_key=family,
             # Phase 4 new fields
             regime_min_edge=regime_min,
+            # Phase 6 new fields — all in log-odds space
+            feat_fg_lo=feat_fg_lo,
+            feat_mom_lo=feat_mom_lo,
+            feat_news_lo=feat_news_lo,
+            feat_mfld_lo=feat_mfld_lo,
+            feat_btc_dom_lo=feat_btc_dom_lo,
         )