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/deobfuscating-powershell-obfuscated-malware/SKILL.md

@@ -1,7 +1,8 @@
 ---
 name: deobfuscating-powershell-obfuscated-malware
-description: Systematically deobfuscate multi-layer PowerShell malware using AST analysis, dynamic tracing, and tools like
-  PSDecode and PowerDecode to reveal hidden payloads and C2 infrastructure.
+description: Systematically deobfuscate multi-layer PowerShell malware using AST analysis,
+  dynamic tracing, and tools like PSDecode and PowerDecode to reveal hidden payloads
+  and C2 infrastructure.
 domain: cybersecurity
 subdomain: malware-analysis
 tags:
@@ -14,8 +15,10 @@ tags:
 - incident-response
 mitre_attack:
 - T1059.001
-- T1027
+- T1027.010
 - T1140
+- T1027
+- T1620
 version: '1.0'
 author: mahipal
 license: Apache-2.0