feat: adopt Phase 3 gate and paper-trade exit policy

Production strategy change based on the July 2026 backtest: paper trades now default to a 30-trading-day hold with the initial stop (classic momentum hold-and-rerank), while target and trailing exits remain available in Admin. The exit policy API/UI now carries hold_days and close_reason can be 'time'.

The activation confidence floor default is now 0/off because the gate ablation showed it added no per-trade edge while filtering out usable setups. Migration 015 clears stored activation_min_confidence and paper_exit_mode so the new defaults take effect; this intentionally resets Track Record comparability from this deploy.

Verification: 451 backend tests pass, ruff check app/ clean, frontend npm run build clean.

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

app/services/paper_trade_service.py

@@ -20,19 +20,26 @@ from app.services.outcome_service import (
     evaluate_setup_against_bars,
 )
 
-# Exit policy for OPEN paper trades (auto-close). "trailing" rides a trailing stop
-# (validated as the best exit in the backtest); "target" closes at the setup's
-# stop/target. Stored in SystemSetting so it's tunable + transparent in the UI.
+# Exit policy for OPEN paper trades (auto-close). "time" holds a fixed number of
+# trading days with the initial stop and exits at that day's close — the exit the
+# July 2026 backtest validated (the classic momentum hold-and-re-rank); "trailing"
+# rides a trailing stop; "target" closes at the setup's stop/target. Stored in
+# SystemSetting so it's tunable + transparent in the UI.
 KEY_EXIT_MODE = "paper_exit_mode"
 KEY_TRAILING_PCT = "paper_trailing_pct"
-DEFAULT_EXIT_MODE = "trailing"
+KEY_HOLD_DAYS = "paper_hold_days"
+DEFAULT_EXIT_MODE = "time"
 DEFAULT_TRAILING_PCT = 12.0
+DEFAULT_HOLD_DAYS = 30
+
+_VALID_EXIT_MODES = ("time", "trailing", "target")
 
 
 async def get_exit_policy(db: AsyncSession) -> dict:
-    """Active auto-exit policy: {'mode': 'trailing'|'target', 'trailing_pct': float}."""
+    """Active auto-exit policy:
+    {'mode': 'time'|'trailing'|'target', 'trailing_pct': float, 'hold_days': int}."""
     mode = (await settings_store.get_value(db, KEY_EXIT_MODE, DEFAULT_EXIT_MODE)).strip().lower()
-    if mode not in ("trailing", "target"):
+    if mode not in _VALID_EXIT_MODES:
         mode = DEFAULT_EXIT_MODE
     raw = await settings_store.get_value(db, KEY_TRAILING_PCT, str(DEFAULT_TRAILING_PCT))
     try:
@@ -40,22 +47,36 @@ async def get_exit_policy(db: AsyncSession) -> dict:
     except (TypeError, ValueError):
         pct = DEFAULT_TRAILING_PCT
     pct = max(0.5, min(90.0, pct))
-    return {"mode": mode, "trailing_pct": pct}
+    raw_days = await settings_store.get_value(db, KEY_HOLD_DAYS, str(DEFAULT_HOLD_DAYS))
+    try:
+        hold_days = int(float(raw_days))
+    except (TypeError, ValueError):
+        hold_days = DEFAULT_HOLD_DAYS
+    hold_days = max(2, min(250, hold_days))
+    return {"mode": mode, "trailing_pct": pct, "hold_days": hold_days}
 
 
 async def set_exit_policy(
-    db: AsyncSession, *, mode: str | None = None, trailing_pct: float | None = None
+    db: AsyncSession,
+    *,
+    mode: str | None = None,
+    trailing_pct: float | None = None,
+    hold_days: int | None = None,
 ) -> dict:
     """Persist the auto-exit policy (admin). Validates inputs."""
     if mode is not None:
         mode = mode.strip().lower()
-        if mode not in ("trailing", "target"):
-            raise ValidationError("mode must be 'trailing' or 'target'")
+        if mode not in _VALID_EXIT_MODES:
+            raise ValidationError("mode must be 'time', 'trailing' or 'target'")
         await settings_store.upsert_setting(db, KEY_EXIT_MODE, mode)
     if trailing_pct is not None:
         if not 0.5 <= float(trailing_pct) <= 90.0:
             raise ValidationError("trailing_pct must be between 0.5 and 90")
         await settings_store.upsert_setting(db, KEY_TRAILING_PCT, str(float(trailing_pct)))
+    if hold_days is not None:
+        if not 2 <= int(hold_days) <= 250:
+            raise ValidationError("hold_days must be between 2 and 250")
+        await settings_store.upsert_setting(db, KEY_HOLD_DAYS, str(int(hold_days)))
     await db.commit()
     return await get_exit_policy(db)
 
@@ -101,6 +122,23 @@ async def _max_high_after(db: AsyncSession, ticker_id: int, since: date) -> floa
     return float(v) if v is not None else None
 
 
+def _time_close(
+    direction: str, init_stop: float, hold_days: int, rows: list[tuple]
+) -> tuple[float, date, str] | None:
+    """Walk post-entry ``rows`` of (date, open, high, low, close); close at the
+    initial stop if hit (a gap through it fills at the open, matching the
+    backtest's fill model), else at the ``hold_days``-th bar's close ('time').
+    None while neither has happened."""
+    long = direction == "long"
+    for i, (d, open_, high, low, close) in enumerate(rows):
+        if (low <= init_stop) if long else (high >= init_stop):
+            fill = min(init_stop, open_) if long else max(init_stop, open_)
+            return float(fill), d, "stop"
+        if i + 1 >= hold_days:
+            return float(close), d, "time"
+    return None
+
+
 def _trailing_close(
     direction: str, entry: float, init_stop: float, trail_frac: float, bars: list[Bar]
 ) -> tuple[float, date, str] | None:
@@ -297,12 +335,12 @@ async def close_trade(
 
 
 async def resolve_open_trades(db: AsyncSession) -> int:
-    """Auto-close open trades whose stop or target was hit in the daily bars.
+    """Auto-close open trades per the active exit policy, from the daily bars.
 
-    Walks the bars after each trade's open (same logic as the outcome evaluator).
-    Target hit → close at the target; stop (or an ambiguous same-bar touch) →
-    close at the stop. Trades that have hit neither stay open. Returns the count
-    closed.
+    Walks the bars after each trade's open. 'time' closes at the initial stop or
+    the hold_days-th close; 'trailing' at the trailing/initial stop; 'target' at
+    the setup's target or stop (same logic as the outcome evaluator). Trades that
+    have hit nothing stay open. Returns the count closed.
     """
     result = await db.execute(select(PaperTrade).where(PaperTrade.status == "open"))
     open_trades = list(result.scalars().all())
@@ -312,22 +350,32 @@ async def resolve_open_trades(db: AsyncSession) -> int:
     policy = await get_exit_policy(db)
     mode = policy["mode"]
     trail_frac = policy["trailing_pct"] / 100.0
+    hold_days = policy["hold_days"]
 
     closed = 0
     for trade in open_trades:
         bars_result = await db.execute(
-            select(OHLCVRecord.date, OHLCVRecord.high, OHLCVRecord.low)
+            select(
+                OHLCVRecord.date, OHLCVRecord.open, OHLCVRecord.high,
+                OHLCVRecord.low, OHLCVRecord.close,
+            )
             .where(
                 OHLCVRecord.ticker_id == trade.ticker_id,
                 OHLCVRecord.date > trade.opened_at.date(),
             )
             .order_by(OHLCVRecord.date.asc())
         )
-        bars = [Bar(date=d, high=h, low=lo) for d, h, lo in bars_result.all()]
+        rows = bars_result.all()
+        bars = [Bar(date=d, high=h, low=lo) for d, _, h, lo, _ in rows]
         if not bars:
             continue
 
-        if mode == "trailing":
+        if mode == "time":
+            hit = _time_close(trade.direction, trade.stop_loss, hold_days, rows)
+            if hit is None:
+                continue  # neither the stop nor the hold horizon reached yet
+            close_price, close_date, reason = hit
+        elif mode == "trailing":
             hit = _trailing_close(trade.direction, trade.entry_price, trade.stop_loss, trail_frac, bars)
             if hit is None:
                 continue  # neither the trailing nor the initial stop reached yet