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/detecting-living-off-the-land-attacks/SKILL.md

@@ -1,15 +1,25 @@
 ---
 name: detecting-living-off-the-land-attacks
-description: >
-  Detect abuse of legitimate Windows binaries (LOLBins) used for living off
-  the land attacks. Monitors process creation, command-line arguments, and
-  parent-child relationships to identify suspicious LOLBin execution patterns.
+description: 'Detect abuse of legitimate Windows binaries (LOLBins) used for living off the land attacks. Monitors process
+  creation, command-line arguments, and parent-child relationships to identify suspicious LOLBin execution patterns.
+
+  '
 domain: cybersecurity
 subdomain: threat-detection
-tags: [lolbins, lotl, fileless-attacks, process-monitoring]
-version: "1.0"
+tags:
+- lolbins
+- lotl
+- fileless-attacks
+- process-monitoring
+version: '1.0'
 author: mahipal
 license: Apache-2.0
+d3fend_techniques:
+- Application Protocol Command Analysis
+- Network Isolation
+- Network Traffic Analysis
+- Client-server Payload Profiling
+- Network Traffic Community Deviation
 ---
 
 # Detecting Living Off the Land Attacks