fix: rename aso-audit to aso

- Rename skills/aso-audit/ directory to skills/aso/
- Update name field in frontmatter
- Update marketplace.json reference

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

.claude-plugin/marketplace.json

@@ -19,7 +19,7 @@
         "./skills/ab-test-setup",
         "./skills/ad-creative",
         "./skills/ai-seo",
-        "./skills/aso-audit",
+        "./skills/aso",
         "./skills/analytics-tracking",
         "./skills/churn-prevention",
         "./skills/cold-email",