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/implementing-gdpr-data-protection-controls/SKILL.md

@@ -1,7 +1,8 @@
 ---
 name: implementing-gdpr-data-protection-controls
-description: The General Data Protection Regulation (EU) 2016/679 (GDPR) is the EU's comprehensive data protection law governing
-  the collection, processing, storage, and transfer of personal data. This skill cover
+description: The General Data Protection Regulation (EU) 2016/679 (GDPR) is the EU's
+  comprehensive data protection law governing the collection, processing, storage,
+  and transfer of personal data. This skill cover
 domain: cybersecurity
 subdomain: compliance-governance
 tags:
@@ -30,6 +31,10 @@ atlas_techniques:
 - AML.T0070
 - AML.T0066
 - AML.T0082
+mitre_attack:
+- T1078
+- T1530
+- T1685.002
 ---
 # Implementing GDPR Data Protection Controls