fix: remove stale enabledPlugins references from settings

Remove engineering-skills and skill-creator plugin references
that no longer exist in their respective marketplaces.

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

.claude/settings.json

@@ -1,6 +1,10 @@
 {
-  "permissions"      : {"read": true, "write": true, "execute": true},
-  "enabledPlugins"   : {"engineering-skills@claude-code-skills": true, "skill-creator@daymade-skills": true},
-  "plansDirectory"   : "/workspaces/claude-marketplace/.claude/plans",
+  "permissions": {
+    "read": true,
+    "write": true,
+    "execute": true
+  },
+  "enabledPlugins": {},
+  "plansDirectory": "/workspaces/claude-marketplace/.claude/plans",
   "bypassPermissions": true
 }