feat: add safe stale branch cleanup to duplicate PR manager

scripts/cleanup-duplicate-prs.sh

@@ -168,3 +168,62 @@ else
 fi
 
 log "Script complete"
+
+# ─── Stale Branch Cleanup ─────────────────────────────────
+# Clean up branches from closed (unmerged) PRs and merged PRs
+log "Checking for stale branches from closed/merged PRs..."
+
+# Get all open PRs to avoid deleting active branches
+OPEN_BRANCHES=$(curl -s -H "$AUTH" "$API/repos/$REPO/pulls?state=open&limit=100" | jq -r '.[] | .head.ref' | sort -u)
+
+# Get all closed PRs (last 100)
+CLOSED_PRS=$(curl -s -H "$AUTH" "$API/repos/$REPO/pulls?state=closed&limit=100")
+
+if [ -n "$CLOSED_PRS" ] && [ "$CLOSED_PRS" != "null" ]; then
+    STALE_BRANCHES=$(echo "$CLOSED_PRS" | jq -r '.[] | select(.merged == false) | .head.ref' | sort -u)
+    MERGED_BRANCHES=$(echo "$CLOSED_PRS" | jq -r '.[] | select(.merged == true) | .head.ref' | sort -u)
+
+    STALE_COUNT=0
+    for branch in $STALE_BRANCHES; do
+        # Skip main/master/develop
+        case "$branch" in main|master|develop|HEAD) continue ;; esac
+        
+        # SAFETY CHECK: Skip if branch is still used by an open PR
+        if echo "$OPEN_BRANCHES" | grep -q "^$branch$"; then
+            log "Skipping branch '$branch' - still has an open PR"
+            continue
+        fi
+
+        if [ "$DRY_RUN" = "true" ]; then
+            log "DRY RUN: Would delete stale branch '$branch' (from closed unmerged PR)"
+        else
+            curl -s -X DELETE -H "$AUTH" "$API/repos/$REPO/branches/$branch" > /dev/null 2>&1 || true
+            log "Deleted stale branch: $branch"
+        fi
+        STALE_COUNT=$((STALE_COUNT + 1))
+    done
+
+    MERGED_COUNT=0
+    for branch in $MERGED_BRANCHES; do
+        case "$branch" in main|master|develop|HEAD) continue ;; esac
+        
+        if echo "$OPEN_BRANCHES" | grep -q "^$branch$"; then
+            log "Skipping branch '$branch' - still has an open PR"
+            continue
+        fi
+
+        if [ "$DRY_RUN" = "true" ]; then
+            log "DRY RUN: Would delete merged branch '$branch'"
+        else
+            curl -s -X DELETE -H "$AUTH" "$API/repos/$REPO/branches/$branch" > /dev/null 2>&1 || true
+            log "Deleted merged branch: $branch"
+        fi
+        MERGED_COUNT=$((MERGED_COUNT + 1))
+    done
+
+    log "Stale branch cleanup:"
+    log "  Closed (unmerged) branches: $STALE_COUNT"
+    log "  Merged branches: $MERGED_COUNT"
+else
+    log "Could not fetch closed PRs for branch cleanup"
+fi