chore(analysis): dedup engine gate PORT06 + drift monitor giornaliero + impact bfill

- _port06_gate_common.py: build_trades_variant/equity_from_trades/port_metrics/dd
  fattorizzati dai 3 gate exit16/trendmax/dip01 (-214 righe duplicate). Nessun
  copy-drift trovato; versione promossa = trendmax (superset con hurst_mask).
  Output dei 3 gate verificato BYTE-IDENTICO prima/dopo. dip_trades resta nel suo
  script (sibling deliberato long-only/orig_gap, non una copia).
- drift_monitor.py: rolling-return per famiglia vs distribuzione storica propria
  (warn sotto p5; oggi: FADE 120g al p2). In crontab host giornaliero 07:15 UTC
  con report Telegram. Osservabilita', non filtro di trading.
- daily_equity_bfill_impact.py: bug bfill _daily_equity QUANTIFICATO -> non
  materiale (OOS invariato per costruzione, FULL DD 3.46->3.67 col fix, nessun
  verdetto gate a rischio). Lasciato documentato in TODO, niente fix.

Co-Authored-By: Claude Fable 5 <noreply@anthropic.com>

scripts/analysis/dip01_exit16_impact.py

@@ -33,11 +33,9 @@ sys.path.insert(0, str(PROJECT_ROOT))
 
 from src.data.downloader import load_data
 from scripts.analysis.strategy_research import atr
-from scripts.analysis.combine_portfolio import (
-    _norm, IDX, port_returns, metrics, SPLIT, OOS_DATE,
-)
+from scripts.analysis.combine_portfolio import _norm, IDX, metrics, SPLIT, OOS_DATE
+from scripts.analysis._port06_gate_common import port_metrics
 from scripts.portfolios._defs import PORTFOLIOS
-from src.portfolio import weighting as W
 
 FEE_RT, LEV, POS, INIT = 0.001, 3.0, 0.15, 1000.0
 BUFFER = 0.5
@@ -139,15 +137,6 @@ def cell_metrics(eq):
     return metrics(dr), metrics(dr, lo=SPLIT)
 
 
-def port_metrics(members, p):
-    ids = p.sleeve_ids
-    dr = pd.DataFrame({i: members[i].pct_change().fillna(0.0) for i in ids})
-    w = W.weight_vector(p.weighting, ids, dr, weights=p.weights,
-                        caps=p.caps, clusters=p.clusters, lookback=p.vol_lookback)
-    drp = port_returns({i: members[i] for i in ids}, w)
-    return metrics(drp), metrics(drp, lo=SPLIT)
-
-
 def main():
     p = PORTFOLIOS["PORT06"]
     print("=" * 104)