feat: show max-hold session countdown

app/schemas/paper_trade.py

@@ -53,3 +53,7 @@ class PaperTradeResponse(BaseModel):
     # when the trailing exit policy is active.
     trailing_stop: float | None = None
     trailing_distance_pct: float | None = None
+    # Trading sessions represented by post-entry OHLCV bars. These are populated
+    # only while the active exit policy has a max-hold rule.
+    sessions_held: int | None = None
+    sessions_remaining: int | None = None

app/services/paper_trade_service.py

@@ -352,6 +352,7 @@ def _to_dict(
     current_price: float | None,
     benchmark_closes: dict[date, float] | None = None,
     trailing: tuple[float, float | None] | None = None,
+    holding_sessions: tuple[int, int] | None = None,
 ) -> dict:
     # For open trades, mark to market; for closed, the realized exit price.
     ref = current_price if trade.status == "open" else trade.close_price
@@ -395,6 +396,8 @@ def _to_dict(
         "fill_mode": trade.fill_mode,
         "trailing_stop": trailing[0] if trailing else None,
         "trailing_distance_pct": trailing[1] if trailing else None,
+        "sessions_held": holding_sessions[0] if holding_sessions else None,
+        "sessions_remaining": holding_sessions[1] if holding_sessions else None,
     }
 
 
@@ -435,6 +438,26 @@ async def list_trades(
     # Current trailing-stop level + distance for open trades (when a trailing
     # policy is active).
     policy = await get_exit_policy(db)
+    holding_sessions: dict[int, tuple[int, int]] = {}
+    if policy["mode"] in ("time", "atr_trailing"):
+        hold_days = int(policy["hold_days"])
+        for t, _ in rows:
+            if t.status != "open":
+                continue
+            held = int(
+                (
+                    await db.execute(
+                        select(func.count())
+                        .select_from(OHLCVRecord)
+                        .where(
+                            OHLCVRecord.ticker_id == t.ticker_id,
+                            OHLCVRecord.date > t.opened_at.date(),
+                        )
+                    )
+                ).scalar_one()
+            )
+            holding_sessions[t.id] = (held, max(0, hold_days - held))
+
     trailing_info: dict[int, tuple[float, float | None]] = {}
     if policy["mode"] == "trailing":
         trail_frac = policy["trailing_pct"] / 100.0
@@ -483,7 +506,14 @@ async def list_trades(
             trailing_info[t.id] = (level, dist)
 
     return [
-        _to_dict(t, sym, prices.get(t.ticker_id), benchmark_closes, trailing_info.get(t.id))
+        _to_dict(
+            t,
+            sym,
+            prices.get(t.ticker_id),
+            benchmark_closes,
+            trailing_info.get(t.id),
+            holding_sessions.get(t.id),
+        )
         for t, sym in rows
     ]