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-fileless-malware-techniques/SKILL.md

@@ -1,9 +1,10 @@
 ---
 name: detecting-fileless-malware-techniques
-description: 'Detects and analyzes fileless malware that operates entirely in memory using PowerShell, WMI, .NET reflection,
-  registry-resident payloads, and living-off-the-land binaries (LOLBins) without writing traditional executable files to disk.
-  Activates for requests involving fileless threat detection, in-memory malware investigation, LOLBin abuse analysis, or WMI
-  persistence examination.
+description: 'Detects and analyzes fileless malware that operates entirely in memory
+  using PowerShell, WMI, .NET reflection, registry-resident payloads, and living-off-the-land
+  binaries (LOLBins) without writing traditional executable files to disk. Activates
+  for requests involving fileless threat detection, in-memory malware investigation,
+  LOLBin abuse analysis, or WMI persistence examination.
 
   '
 domain: cybersecurity
@@ -28,6 +29,12 @@ nist_csf:
 - RS.AN-03
 - ID.RA-01
 - DE.CM-01
+mitre_attack:
+- T1027
+- T1055
+- T1140
+- T1497
+- T1547
 ---
 
 # Detecting Fileless Malware Techniques