feat: add NIST CSF 2.0 nist_csf field to all 754 cybersecurity skills

Mapped every skill to NIST CSF 2.0 subcategory IDs (GV/ID/PR/DE/RS/RC functions)
based on subdomain and content analysis. Restores 11 skills corrupted during
prior rebase, re-enriching with ATLAS, D3FEND, NIST AI RMF, and CSF 2.0 fields.

All 754 skills now carry structured mappings for all 5 security frameworks:
- MITRE ATT&CK (in tags)
- MITRE ATLAS v5.5 (atlas_techniques)
- MITRE D3FEND v1.3 (d3fend_techniques)
- NIST AI RMF 1.0 (nist_ai_rmf)
- NIST CSF 2.0 (nist_csf)

skills/implementing-siem-correlation-rules-for-apt/SKILL.md

@@ -1,16 +1,24 @@
 ---
 name: implementing-siem-correlation-rules-for-apt
-description: >-
-  Write multi-event correlation rules that detect APT lateral movement by chaining Windows authentication events,
-  process execution telemetry, and network connection logs across hosts. Uses Splunk SPL and Sigma rule format
-  to correlate Event IDs 4624, 4648, 4688, and Sysmon Events 1/3 within sliding time windows to surface attack
-  sequences invisible to single-event detections.
+description: Write multi-event correlation rules that detect APT lateral movement by chaining Windows authentication events,
+  process execution telemetry, and network connection logs across hosts. Uses Splunk SPL and Sigma rule format to correlate
+  Event IDs 4624, 4648, 4688, and Sysmon Events 1/3 within sliding time windows to surface attack sequences invisible to single-event
+  detections.
 domain: cybersecurity
 subdomain: security-operations
-tags: [implementing, siem, correlation, rules]
-version: "1.0"
+tags:
+- implementing
+- siem
+- correlation
+- rules
+version: '1.0'
 author: mahipal
 license: Apache-2.0
+nist_csf:
+- DE.CM-01
+- RS.MA-01
+- GV.OV-01
+- DE.AE-02
 ---