Fix runner system by checking minimum position size viability

PROBLEM: Runner never activated because Drift force-closes positions below
minimum size. TP2 would close 80% leaving 5% runner (~$105), but Drift
automatically closed the entire position.

SOLUTION:
1. Created runner-calculator.ts with canUseRunner() to check if remaining
   size would be above Drift minimums BEFORE executing TP2 close
2. If runner not viable: Skip TP2 close entirely, activate trailing stop
   on full 25% remaining (from TP1)
3. If runner viable: Execute TP2 as normal, activate trailing on 5%

Benefits:
- Runner system will now actually work for viable position sizes
- Positions that are too small won't try to force-close below minimums
- Better logs showing why runner did/didn't activate
- Trailing stop works on larger % if runner not viable (better R:R)

Example: $2100 position → $525 after TP1 → $105 runner = VIABLE
         $4 ETH position → $1 after TP1 → $0.20 runner = NOT VIABLE

Runner will trail with ATR-based dynamic % (0.25-0.9%) below peak price.

lib/trading/position-manager.ts

@@ -9,6 +9,7 @@ import { closePosition } from '../drift/orders'
 import { getPythPriceMonitor, PriceUpdate } from '../pyth/price-monitor'
 import { getMergedConfig, TradingConfig, getMarketConfig } from '../../config/trading'
 import { updateTradeExit, updateTradeState, getOpenTrades } from '../database/trades'
+import { canUseRunner, getViableTP2Percent } from './runner-calculator'
 
 export interface ActiveTrade {
   id: string
@@ -707,9 +708,37 @@ export class PositionManager {
     if (trade.tp1Hit && !trade.tp2Hit && this.shouldTakeProfit2(currentPrice, trade)) {
       console.log(`🎊 TP2 HIT: ${trade.symbol} at ${profitPercent.toFixed(2)}%`)
       
-      // Calculate how much to close based on TP2 size percent
+      // Check if runner would be viable with current position size
+      const runnerCheck = canUseRunner(
+        trade.symbol,
+        trade.currentSize,
+        currentPrice,
+        this.config.takeProfit1SizePercent,
+        this.config.takeProfit2SizePercent
+      )
+      
+      if (!runnerCheck.viable) {
+        console.log(`⚠️ Runner not viable: ${runnerCheck.reason}`)
+        console.log(`   Skipping TP2 close, will use trailing stop on full 25% remaining`)
+        
+        // Mark TP2 as "hit" but don't close anything - activate trailing on full 25%
+        trade.tp2Hit = true
+        trade.trailingStopActive = true
+        trade.runnerTrailingPercent = this.getRunnerTrailingPercent(trade)
+        
+        console.log(
+          `🏃 Runner activated on full remaining position: ${((trade.currentSize / trade.positionSize) * 100).toFixed(1)}% | trailing buffer ${trade.runnerTrailingPercent?.toFixed(3)}%`
+        )
+        
+        await this.saveTradeState(trade)
+        return
+      }
+      
+      // Runner is viable - proceed with TP2 close
       const percentToClose = this.config.takeProfit2SizePercent
       
+      console.log(`✅ Runner viable: ${runnerCheck.runnerSizeBase.toFixed(4)} base (${runnerCheck.runnerSizeUSD.toFixed(2)} USD)`)
+      
       await this.executeExit(trade, percentToClose, 'TP2', currentPrice)
       
       // If some position remains, mark TP2 as hit and activate trailing stop