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/performing-insider-threat-investigation/references/api-reference.md

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+# API Reference: Insider Threat Investigation
+
+## Data Sources
+
+| Source | Log Type | Key Fields |
+|--------|----------|------------|
+| DLP System | File transfers, USB connections | user, action, file_path, bytes, device_id |
+| Email Gateway | Sent/received/forwarded emails | sender, recipient, subject, attachment_size |
+| VPN / Auth Logs | Authentication events | user, timestamp, source_ip, result |
+| Cloud Access Broker | SaaS application activity | user, app, action, data_volume |
+| Badge Access | Physical access events | user, location, timestamp, direction |
+
+## Microsoft Graph API (for Microsoft 365 environments)
+
+| Endpoint | Method | Description |
+|----------|--------|-------------|
+| `/auditLogs/signIns` | GET | User sign-in activity logs |
+| `/security/alerts` | GET | Security alerts including DLP |
+| `/users/{id}/activities` | GET | User activity feed |
+| `/users/{id}/mailFolders/{id}/messages` | GET | Email messages (eDiscovery) |
+
+## Exabeam UEBA API
+
+| Endpoint | Description |
+|----------|-------------|
+| `/api/users/{user}/timeline` | User activity timeline with risk scores |
+| `/api/users/{user}/risk` | Current risk score and contributing factors |
+
+## Python Libraries
+
+| Library | Version | Purpose |
+|---------|---------|---------|
+| `csv` | stdlib | Parse exported log files |
+| `json` | stdlib | Report generation and data exchange |
+| `datetime` | stdlib | Timestamp parsing and time-window analysis |
+| `requests` | >=2.28 | API access for UEBA and SIEM platforms |
+
+## References
+
+- CISA Insider Threat Guide: https://www.cisa.gov/topics/physical-security/insider-threat-mitigation
+- NIST SP 800-53 (PS-6 Access Agreements): https://csrc.nist.gov/publications/detail/sp/800-53/rev-5/final
+- Microsoft Purview Insider Risk: https://learn.microsoft.com/en-us/purview/insider-risk-management
+- MITRE Insider Threat: https://attack.mitre.org/techniques/T1078/