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-api-schema-validation-security/SKILL.md

@@ -1,12 +1,26 @@
 ---
 name: implementing-api-schema-validation-security
-description: Implement API schema validation using OpenAPI specifications and JSON Schema to enforce input/output contracts and prevent injection, data exposure, and mass assignment attacks.
+description: Implement API schema validation using OpenAPI specifications and JSON Schema to enforce input/output contracts
+  and prevent injection, data exposure, and mass assignment attacks.
 domain: cybersecurity
 subdomain: api-security
-tags: [api-security, schema-validation, openapi, json-schema, input-validation, data-leakage-prevention, mass-assignment, api-gateway]
-version: "1.0"
+tags:
+- api-security
+- schema-validation
+- openapi
+- json-schema
+- input-validation
+- data-leakage-prevention
+- mass-assignment
+- api-gateway
+version: '1.0'
 author: mahipal
 license: Apache-2.0
+nist_csf:
+- PR.PS-01
+- ID.RA-01
+- PR.DS-10
+- DE.CM-01
 ---
 
 # Implementing API Schema Validation Security