ci: workspace mcpp bootstrap pin -> 0.0.58 (released + indexed)

v0.0.58 released (mcpp-community/mcpp), mirrored to xlings-res/mcpp@0.0.58
(github + gitcode, byte-identical), and registered as latest in
openxlings/xim-pkgindex. xlings install mcpp@0.0.58 verified end-to-end.

Author: Sunrisepeak

.xlings.json

@@ -1,5 +1,5 @@
 {
   "workspace": {
-    "mcpp": "0.0.57"
+    "mcpp": "0.0.58"
   }
 }