Map all 754 skills to MITRE ATT&CK v19.1

- Add validated mitre_attack frontmatter to all 754 skills (286 distinct
  techniques), verified against MITRE ATT&CK v19.1 via the official
  mitreattack-python library: 0 revoked, deprecated, or invalid IDs
- Curate precise per-skill technique IDs for forensics, malware-analysis,
  threat-intel, and red-team skills (e.g. DCSync -> T1003.006,
  Kerberoasting -> T1558.003, Pass-the-Ticket -> T1550.003)
- Reconcile v19.1 tactic restructuring: Defense Evasion split into
  Stealth (TA0005) and Defense Impairment (TA0112); revoked T1562.*
  family and T1070.001/.002 remapped to active equivalents (T1685.*)
- Normalize word-split tags across 35 skills (remove filename-derived
  stopword tags, add semantic cybersecurity tags)
- Add api-reference.md for 3 skills that were missing it
- Update README ATT&CK section with accurate v19.1 tactic distribution

skills/securing-api-gateway-with-aws-waf/SKILL.md

@@ -1,8 +1,9 @@
 ---
 name: securing-api-gateway-with-aws-waf
-description: 'Securing API Gateway endpoints with AWS WAF by configuring managed rule groups for OWASP Top 10 protection,
-  creating custom rate limiting rules, implementing bot control, setting up IP reputation filtering, and monitoring WAF metrics
-  for security effectiveness.
+description: 'Securing API Gateway endpoints with AWS WAF by configuring managed rule
+  groups for OWASP Top 10 protection, creating custom rate limiting rules, implementing
+  bot control, setting up IP reputation filtering, and monitoring WAF metrics for
+  security effectiveness.
 
   '
 domain: cybersecurity
@@ -23,6 +24,12 @@ nist_csf:
 - ID.AM-08
 - GV.SC-06
 - DE.CM-01
+mitre_attack:
+- T1078.004
+- T1530
+- T1537
+- T1580
+- T0816
 ---
 
 # Securing API Gateway with AWS WAF