Add folder anatomy (scripts/agent.py + references/api-reference.md) for 648 cybersecurity skills

Complete skill folder anatomy across all cybersecurity skills:
- scripts/agent.py: 80-150 line Python agents using real libraries (impacket,
  boto3, azure-mgmt-*, kubernetes, pefile, yara, scapy, shodan, stix2, etc.)
- references/api-reference.md: real API documentation with method signatures
- LICENSE: MIT license for all skill folders

skills/detecting-kerberoasting-attacks/references/api-reference.md

@@ -0,0 +1,49 @@
+# API Reference: Detecting Kerberoasting Attacks
+
+## python-evtx Library
+```python
+from Evtx.Evtx import FileHeader
+with open("Security.evtx", "rb") as f:
+    fh = FileHeader(f)
+    for record in fh.records():
+        xml_string = record.xml()
+```
+
+## Event ID 4769 - Kerberos TGS Request
+```xml
+<EventData>
+  <Data Name="TargetUserName">svc_sql</Data>
+  <Data Name="ServiceName">MSSQLSvc/db01.corp.local:1433</Data>
+  <Data Name="TicketEncryptionType">0x17</Data>
+  <Data Name="TicketOptions">0x40810000</Data>
+  <Data Name="IpAddress">::ffff:10.0.0.50</Data>
+  <Data Name="Status">0x0</Data>
+</EventData>
+```
+
+## Encryption Type Values
+| Hex | Type | Risk |
+|-----|------|------|
+| 0x17 | RC4-HMAC | Kerberoasting indicator |
+| 0x18 | RC4-HMAC-EXP | Kerberoasting indicator |
+| 0x11 | AES128-CTS-HMAC-SHA1 | Normal |
+| 0x12 | AES256-CTS-HMAC-SHA1 | Normal |
+
+## Detection Logic
+1. Filter Event 4769 where TicketEncryptionType = 0x17 (RC4)
+2. Exclude machine accounts (ServiceName ending in `$`)
+3. Exclude krbtgt service
+4. Alert on high-volume TGS from single source (>10 unique SPNs in 5 min)
+5. Correlate with Event 4624 for source attribution
+
+## Event ID 4624 - Logon Event (Correlation)
+```xml
+<Data Name="TargetUserName">attacker_user</Data>
+<Data Name="LogonType">3</Data>
+<Data Name="IpAddress">10.0.0.50</Data>
+<Data Name="WorkstationName">WORKSTATION1</Data>
+```
+
+## MITRE ATT&CK Mapping
+- T1558.003 - Kerberoasting
+- T1558 - Steal or Forge Kerberos Tickets