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/performing-external-network-penetration-test/SKILL.md

@@ -1,12 +1,27 @@
 ---
 name: performing-external-network-penetration-test
-description: Conduct a comprehensive external network penetration test to identify vulnerabilities in internet-facing infrastructure using PTES methodology, reconnaissance, scanning, exploitation, and reporting.
+description: Conduct a comprehensive external network penetration test to identify vulnerabilities in internet-facing infrastructure
+  using PTES methodology, reconnaissance, scanning, exploitation, and reporting.
 domain: cybersecurity
 subdomain: penetration-testing
-tags: [external-pentest, network-security, PTES, OSSTMM, Nmap, Metasploit, vulnerability-assessment, reconnaissance, exploitation]
-version: "1.0"
+tags:
+- external-pentest
+- network-security
+- PTES
+- OSSTMM
+- Nmap
+- Metasploit
+- vulnerability-assessment
+- reconnaissance
+- exploitation
+version: '1.0'
 author: mahipal
 license: Apache-2.0
+nist_csf:
+- ID.RA-01
+- ID.RA-06
+- GV.OV-02
+- DE.AE-07
 ---
 
 # Performing External Network Penetration Test