update non-reset-packs semantics

res/scripts/stdlib.lua

@@ -186,7 +186,6 @@ events = require "core:internal/events"
 
 function pack.unload(prefix)
     events.remove_by_prefix(prefix)
-    __vc__pack_envs[prefix] = nil
 end
 
 function __vc_start_app_script(path)

res/scripts/stdmin.lua

@@ -771,6 +771,7 @@ function __scripts_cleanup(non_reset_packs)
             __cached_scripts[k] = nil
             package.loaded[k] = nil
         end
+        __vc__pack_envs[packname] = nil
         ::continue::
     end
 end