fix using old mach

internal/shop.cm

@@ -438,6 +438,7 @@ function resolve_mod_fn(path, pkg) {
   var compiled = null
   var mach_path = null
   var mach_blob = null
+  var mcode_path = null
   var ir = null
   var optimized = null
 
@@ -446,7 +447,7 @@ function resolve_mod_fn(path, pkg) {
     return cached
   }
 
-  // Check for pre-compiled .mach file alongside .cm source
+  // Check for pre-compiled .mach or .mcode file alongside .cm source
   if (ends_with(path, '.cm')) {
     mach_path = text(path, 0, length(path) - 3) + '.mach'
     if (fd.is_file(mach_path)) {
@@ -454,6 +455,12 @@ function resolve_mod_fn(path, pkg) {
       put_into_cache(stone(blob(content)), mach_blob)
       return mach_blob
     }
+    mcode_path = path + '.mcode'
+    if (fd.is_file(mcode_path)) {
+      compiled = mach_compile_mcode_bin(path, text(fd.slurp(mcode_path)))
+      put_into_cache(stone(blob(content)), compiled)
+      return compiled
+    }
   }
 
   // Compile via full pipeline: analyze → mcode → streamline → serialize