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/deploying-tailscale-for-zero-trust-vpn/SKILL.md

@@ -1,7 +1,8 @@
 ---
 name: deploying-tailscale-for-zero-trust-vpn
-description: Deploy and configure Tailscale as a WireGuard-based zero trust mesh VPN with identity-aware access controls,
-  ACLs, and exit nodes for secure peer-to-peer connectivity.
+description: Deploy and configure Tailscale as a WireGuard-based zero trust mesh VPN
+  with identity-aware access controls, ACLs, and exit nodes for secure peer-to-peer
+  connectivity.
 domain: cybersecurity
 subdomain: zero-trust-architecture
 tags:
@@ -22,6 +23,11 @@ nist_csf:
 - PR.AA-05
 - PR.IR-01
 - GV.PO-01
+mitre_attack:
+- T1133
+- T1078
+- T1021
+- T1572
 ---
 
 # Deploying Tailscale for Zero Trust VPN