fix(position-manager): correctly handle partial close size conversions to USD

- Convert closePosition.closedSize (base asset) to USD when updating trade.currentSize
- Fix conversion when position.size detected from Drift: set currentSize = position.size * currentPrice
- Prevent trade.currentSize from being reduced to tiny values due to unit mismatch

lib/trading/position-manager.ts

@@ -450,8 +450,8 @@ export class PositionManager {
       // Position exists but size mismatch (partial close by TP1?)
       if (position.size < trade.currentSize * 0.95) { // 5% tolerance
         console.log(`⚠️ Position size mismatch: expected ${trade.currentSize}, got ${position.size}`)
-        // Update current size to match reality
-        trade.currentSize = position.size * (trade.positionSize / trade.currentSize) // Convert to USD
+        // Update current size to match reality (convert base asset size to USD using current price)
+        trade.currentSize = position.size * currentPrice
         trade.tp1Hit = true
         await this.saveTradeState(trade)
       }
@@ -687,9 +687,13 @@ export class PositionManager {
       } else {
         // Partial close (TP1)
         trade.realizedPnL += result.realizedPnL || 0
-        trade.currentSize -= result.closedSize || 0
-        
-        console.log(`✅ 50% closed | Realized: $${result.realizedPnL?.toFixed(2)} | Remaining: ${trade.currentSize}`)
+        // result.closedSize is returned in base asset units (e.g., SOL), convert to USD using closePrice
+        const closePriceForCalc = result.closePrice || currentPrice
+        const closedSizeBase = result.closedSize || 0
+        const closedUSD = closedSizeBase * closePriceForCalc
+        trade.currentSize = Math.max(0, trade.currentSize - closedUSD)
+
+        console.log(`✅ Partial close executed | Realized: $${(result.realizedPnL || 0).toFixed(2)} | Closed (base): ${closedSizeBase.toFixed(6)} | Closed (USD): $${closedUSD.toFixed(2)} | Remaining USD: $${trade.currentSize.toFixed(2)}`)
       }
 
       // TODO: Send notification