docs: Document runner SL gap as Common Pitfall #27

Added comprehensive documentation of the runner stop loss protection gap:
- Root cause analysis (SL check only before TP1)
- Bug sequence and impact details
- Code fix with examples
- Compounding factors (small runner + no on-chain orders)
- Lesson learned for future risk management code

.github/copilot-instructions.md

@@ -1183,6 +1183,43 @@ trade.realizedPnL += actualRealizedPnL  // NOT: result.realizedPnL from SDK
     - **v6:** HalfTrend + BarColor strategy (Nov 12+)
     - Used for performance comparison between strategies
 
+27. **Runner stop loss gap - NO protection between TP1 and TP2 (CRITICAL - Fixed Nov 15, 2025):**
+    - **Symptom:** Runner position remained open despite price moving far past stop loss level
+    - **Root Cause:** Position Manager only checked stop loss BEFORE TP1 (line 877: `if (!trade.tp1Hit && this.shouldStopLoss(...)`), creating a protection gap
+    - **Bug sequence:**
+      1. SHORT opened, TP1 hit at 70% close (runner = 30% remaining)
+      2. Runner had stop loss at profit-lock level (+0.5%)
+      3. Price moved past stop loss → NO CHECK RAN (tp1Hit = true, so SL check skipped)
+      4. Runner exposed to unlimited loss for hours during TP1→TP2 window
+      5. Made worse by runner below Drift minimum size ($12.79 < $15) = no on-chain orders either
+    - **Impact:** Hours of unprotected runner exposure = potential unlimited loss on 25-30% remaining position
+    - **Code analysis:**
+      ```typescript
+      // Line 877: Stop loss checked ONLY before TP1
+      if (!trade.tp1Hit && this.shouldStopLoss(currentPrice, trade)) {
+        console.log(`🔴 STOP LOSS: ${trade.symbol}`)
+        await this.executeExit(trade, 100, 'SL', currentPrice)
+      }
+      
+      // Lines 881-895: TP1 and TP2 processing - NO STOP LOSS CHECK
+      
+      // BUG: Runner between TP1-TP2 had ZERO stop loss protection!
+      ```
+    - **Fix:** Added explicit runner stop loss check at line ~881:
+    ```typescript
+    // 2b. CRITICAL: Runner stop loss (AFTER TP1, BEFORE TP2)
+    // This protects the runner position after TP1 closes main position
+    if (trade.tp1Hit && !trade.tp2Hit && this.shouldStopLoss(currentPrice, trade)) {
+      console.log(`🔴 RUNNER STOP LOSS: ${trade.symbol} at ${profitPercent.toFixed(2)}% (profit lock triggered)`)
+      await this.executeExit(trade, 100, 'SL', currentPrice)
+      return
+    }
+    ```
+    - **Why undetected:** Runner system relatively new (Nov 11), most trades hit TP2 quickly without price reversals
+    - **Compounded by:** Drift minimum size check ($15 for SOL) prevented on-chain SL orders for small runners
+    - **Log warning:** `⚠️ SL size below market min, skipping on-chain SL` indicates runner has NO on-chain protection
+    - **Lesson:** Every conditional branch in risk management MUST have explicit stop loss checks - never assume "it'll get caught somewhere"
+
 27. **External closure duplicate updates bug (CRITICAL - Fixed Nov 12, 2025):**
     - **Symptom:** Trades showing 7-8x larger losses than actual ($58 loss when Drift shows $7 loss)
     - **Root Cause:** Position Manager monitoring loop re-processes external closures multiple times before trade removed from activeTrades Map
@@ -1212,7 +1249,7 @@ trade.realizedPnL += actualRealizedPnL  // NOT: result.realizedPnL from SDK
     - **Root cause:** Async timing issue - `removeTrade()` is async but monitoring loop continues synchronously
     - **Evidence:** Logs showed 8 consecutive "External closure recorded" messages with increasing P&L
     - **Line:** `lib/trading/position-manager.ts` line 493 (external closure detection block)
-    - Must update `CreateTradeParams` interface when adding new database fields (see pitfall #21)
+    - Must update `CreateTradeParams` interface when adding new database fields (see pitfall #23)
     - Analytics endpoint `/api/analytics/version-comparison` compares v5 vs v6 performance
 
 28. **Signal quality threshold adjustment (Nov 12, 2025):**