feat: enrich 209 skills with MITRE ATLAS, D3FEND, and NIST AI RMF frontmatter

Added structured security framework mappings to SKILL.md frontmatter across all applicable skills:
- atlas_techniques: MITRE ATLAS v5.5 AML.TXXXX IDs (81 skills, AI-targeted attack techniques)
- d3fend_techniques: MITRE D3FEND v1.3 defensive technique labels (139 skills, mapped from ATT&CK IDs)
- nist_ai_rmf: NIST AI RMF 1.0 subcategory IDs (85 skills, AI risk management functions)

Also updates ATTACK_COVERAGE.md with coverage statistics for all three frameworks.

skills/conducting-social-engineering-penetration-test/SKILL.md

@@ -1,12 +1,28 @@
 ---
 name: conducting-social-engineering-penetration-test
-description: Design and execute a social engineering penetration test including phishing, vishing, smishing, and physical pretexting campaigns to measure human security resilience and identify training gaps.
+description: Design and execute a social engineering penetration test including phishing, vishing, smishing, and physical
+  pretexting campaigns to measure human security resilience and identify training gaps.
 domain: cybersecurity
 subdomain: penetration-testing
-tags: [social-engineering, phishing, vishing, pretexting, GoPhish, SET, OSINT, security-awareness, red-team]
-version: "1.0"
+tags:
+- social-engineering
+- phishing
+- vishing
+- pretexting
+- GoPhish
+- SET
+- OSINT
+- security-awareness
+- red-team
+version: '1.0'
 author: mahipal
 license: Apache-2.0
+atlas_techniques:
+- AML.T0088
+- AML.T0052
+nist_ai_rmf:
+- GOVERN-6.2
+- MAP-5.2
 ---
 
 # Conducting Social Engineering Penetration Test