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/hunting-for-lolbins-execution-in-endpoint-logs/SKILL.md

@@ -1,12 +1,26 @@
 ---
 name: hunting-for-lolbins-execution-in-endpoint-logs
-description: Hunt for adversary abuse of Living Off the Land Binaries (LOLBins) by analyzing endpoint process creation logs for suspicious execution patterns of legitimate Windows system binaries used for malicious purposes.
+description: Hunt for adversary abuse of Living Off the Land Binaries (LOLBins) by analyzing endpoint process creation logs
+  for suspicious execution patterns of legitimate Windows system binaries used for malicious purposes.
 domain: cybersecurity
 subdomain: threat-hunting
-tags: [threat-hunting, lolbins, living-off-the-land, endpoint-detection, process-monitoring, mitre-t1218, defense-evasion]
-version: "1.0"
+tags:
+- threat-hunting
+- lolbins
+- living-off-the-land
+- endpoint-detection
+- process-monitoring
+- mitre-t1218
+- defense-evasion
+version: '1.0'
 author: mahipal
 license: Apache-2.0
+d3fend_techniques:
+- Executable Denylisting
+- Execution Isolation
+- File Metadata Consistency Validation
+- Application Protocol Command Analysis
+- Content Format Conversion
 ---
 
 # Hunting for LOLBins Execution in Endpoint Logs