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/reverse-engineering-ransomware-encryption-routine/SKILL.md

@@ -1,12 +1,27 @@
 ---
 name: reverse-engineering-ransomware-encryption-routine
-description: Reverse engineer ransomware encryption routines to identify cryptographic algorithms, key generation flaws, and potential decryption opportunities using static and dynamic analysis.
+description: Reverse engineer ransomware encryption routines to identify cryptographic algorithms, key generation flaws, and
+  potential decryption opportunities using static and dynamic analysis.
 domain: cybersecurity
 subdomain: malware-analysis
-tags: [ransomware, encryption, reverse-engineering, cryptanalysis, aes, rsa, decryption, malware-analysis]
-version: "1.0"
+tags:
+- ransomware
+- encryption
+- reverse-engineering
+- cryptanalysis
+- aes
+- rsa
+- decryption
+- malware-analysis
+version: '1.0'
 author: mahipal
 license: Apache-2.0
+d3fend_techniques:
+- File Metadata Consistency Validation
+- Content Format Conversion
+- File Content Analysis
+- Platform Hardening
+- File Format Verification
 ---
 # Reverse Engineering Ransomware Encryption Routine