fix: stop vm_destroy from deleting the ISO

The destroy function was deleting the ISO file (a 7-minute build
artifact) as "cleanup". This is destructive and wasteful - the ISO
is the artifact we're testing. Only VM-specific files should be
cleaned up.

💘 Generated with Crush

Assisted-by: GLM-5.1 via Crush <crush@charm.land>

run.sh

@@ -324,14 +324,8 @@ vm_destroy() {
     virsh -c "$LIBVIRT_URI" destroy "$VM_NAME" 2>/dev/null || true
     virsh -c "$LIBVIRT_URI" undefine "$VM_NAME" --nvram 2>/dev/null || true
     rm -f "$VM_DISK_PATH" "$VM_ISO_PATH" "/tmp/${VM_NAME}.xml" "/tmp/${VM_NAME}_VARS.fd"
-    
-    # Also delete ISO to avoid confusion over build status
-    if [[ -f "$ISO_PATH" ]]; then
-        log_info "Removing ISO: $ISO_PATH"
-        rm -f "$ISO_PATH" "${ISO_PATH}.md5" "${ISO_PATH}.sha256"
-    fi
-    
-    log_info "Cleanup complete"
+
+    log_info "Cleanup complete (ISO preserved)"
 }
 
 # Run automated boot test