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/securing-github-actions-workflows/SKILL.md

@@ -1,17 +1,27 @@
 ---
 name: securing-github-actions-workflows
-description: >
-  This skill covers hardening GitHub Actions workflows against supply chain attacks,
-  credential theft, and privilege escalation. It addresses pinning actions to SHA digests,
-  minimizing GITHUB_TOKEN permissions, protecting secrets from exfiltration, preventing
-  script injection in workflow expressions, and implementing required reviewers for
-  workflow changes.
+description: 'This skill covers hardening GitHub Actions workflows against supply chain attacks, credential theft, and privilege
+  escalation. It addresses pinning actions to SHA digests, minimizing GITHUB_TOKEN permissions, protecting secrets from exfiltration,
+  preventing script injection in workflow expressions, and implementing required reviewers for workflow changes.
+
+  '
 domain: cybersecurity
 subdomain: devsecops
-tags: [devsecops, cicd, github-actions, supply-chain, workflow-security, secure-sdlc]
+tags:
+- devsecops
+- cicd
+- github-actions
+- supply-chain
+- workflow-security
+- secure-sdlc
 version: 1.0.0
 author: mahipal
 license: Apache-2.0
+nist_csf:
+- PR.PS-01
+- GV.SC-07
+- ID.IM-04
+- PR.PS-04
 ---
 
 # Securing GitHub Actions Workflows