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-purdue-model-network-segmentation/SKILL.md

@@ -1,8 +1,9 @@
 ---
 name: implementing-purdue-model-network-segmentation
-description: 'Implement network segmentation based on the Purdue Enterprise Reference Architecture (PERA) model to separate
-  industrial control system networks into hierarchical security zones from Level 0 physical process through Level 5 enterprise,
-  enforcing strict traffic control between OT and IT domains.
+description: 'Implement network segmentation based on the Purdue Enterprise Reference
+  Architecture (PERA) model to separate industrial control system networks into hierarchical
+  security zones from Level 0 physical process through Level 5 enterprise, enforcing
+  strict traffic control between OT and IT domains.
 
   '
 domain: cybersecurity
@@ -24,6 +25,12 @@ nist_csf:
 - DE.CM-01
 - ID.AM-05
 - GV.OC-02
+mitre_attack:
+- T1078
+- T1190
+- T1059
+- T0816
+- T0836
 ---
 
 # Implementing Purdue Model Network Segmentation