fix: Use macOS bash 3 compatible string capitalization

Replace ${skin^} (bash 4+) with sed command for cross-platform compatibility

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Co-Authored-By: Claude Opus 4.5 <noreply@anthropic.com>

scripts/dss-init.sh

@@ -87,13 +87,15 @@ EOF
 
   # Reset skins
   for skin in base classic workbench; do
+    # Capitalize first letter (macOS bash 3 compatible)
+    skin_cap="$(echo "$skin" | sed 's/./\U&/')"
     if [ "$skin" = "base" ]; then
       cat > "dss-claude-plugin/core/skins/${skin}.json" << EOF
 {
   "meta": {
     "id": "${skin}",
     "version": "1.0.0",
-    "description": "${skin^} skin - awaiting Figma sync"
+    "description": "${skin_cap} skin - awaiting Figma sync"
   },
   "tokens": {}
 }
@@ -104,7 +106,7 @@ EOF
   "meta": {
     "id": "${skin}",
     "version": "1.0.0",
-    "description": "${skin^} skin - awaiting Figma sync",
+    "description": "${skin_cap} skin - awaiting Figma sync",
     "extends": "base"
   },
   "tokens": {}