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/detecting-rootkit-activity/SKILL.md

@@ -1,9 +1,10 @@
 ---
 name: detecting-rootkit-activity
-description: 'Detects rootkit presence on compromised systems by identifying hidden processes, hooked system calls, modified
-  kernel structures, hidden files, and covert network connections using memory forensics, cross-view detection, and integrity
-  checking techniques. Activates for requests involving rootkit detection, hidden process discovery, kernel integrity checking,
-  or system call hook analysis.
+description: 'Detects rootkit presence on compromised systems by identifying hidden
+  processes, hooked system calls, modified kernel structures, hidden files, and covert
+  network connections using memory forensics, cross-view detection, and integrity
+  checking techniques. Activates for requests involving rootkit detection, hidden
+  process discovery, kernel integrity checking, or system call hook analysis.
 
   '
 domain: cybersecurity
@@ -22,6 +23,11 @@ nist_csf:
 - RS.AN-03
 - ID.RA-01
 - DE.CM-01
+mitre_attack:
+- T1014
+- T1547.006
+- T1564.001
+- T1574.006
 ---
 
 # Detecting Rootkit Activity