docs: add Docker cleanup instructions to prevent disk full issues

- Document build cache accumulation problem (40-50 GB typical)
- Add cleanup commands: image prune, builder prune, volume prune
- Recommend running after each deployment or weekly
- Typical space freed: 40-55 GB per cleanup
- Clarify what's safe vs not safe to delete
- Part of maintaining healthy development environment

.github/copilot-instructions.md

@@ -292,6 +292,49 @@ docker logs trading-bot-v4 | grep "Server starting" | head -1
 
 **DO NOT use:** `docker compose build trading-bot` in foreground - one network hiccup kills 60s of work
 
+### Docker Cleanup After Builds
+
+**CRITICAL: Prevent disk full issues from build cache accumulation**
+
+Docker builds create intermediate layers (1.3+ GB per build) that accumulate over time. Build cache can reach 40-50 GB after frequent rebuilds.
+
+**After successful deployment, clean up:**
+```bash
+# Remove dangling images (old builds)
+docker image prune -f
+
+# Remove build cache (biggest space hog - 40+ GB typical)
+docker builder prune -f
+
+# Optional: Remove dangling volumes (if no important data)
+docker volume prune -f
+
+# Check space saved
+docker system df
+```
+
+**When to run:**
+- After each successful deployment (recommended)
+- Weekly if building frequently
+- When disk space warnings appear
+- Before major updates/migrations
+
+**Space typically freed:**
+- Dangling images: 2-5 GB
+- Build cache: 40-50 GB
+- Dangling volumes: 0.5-1 GB
+- **Total: 40-55 GB per cleanup**
+
+**What's safe to delete:**
+- `<none>` tagged images (old builds)
+- Build cache (recreated on next build)
+- Dangling volumes (orphaned from removed containers)
+
+**What NOT to delete:**
+- Named volumes (contain data: `trading-bot-postgres`, etc.)
+- Active containers
+- Tagged images currently in use
+
 ---
 
 ## Critical Components

lib/startup/init-position-manager.ts

@@ -109,7 +109,7 @@ async function validateOpenTrades() {
         }
         
         // Position EXISTS on Drift
-        const driftDirection = position.direction.toLowerCase() as 'long' | 'short'
+        const driftDirection = position.side.toLowerCase() as 'long' | 'short'
         
         if (driftDirection !== trade.direction) {
           console.log(`⚠️ DIRECTION MISMATCH: ${trade.symbol} DB=${trade.direction} Drift=${driftDirection}`)