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/testing-for-broken-access-control/references/api-reference.md

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+# API Reference: Testing for Broken Access Control
+
+## requests Library
+
+### Authentication Patterns
+```python
+# Bearer token authentication
+headers = {"Authorization": "Bearer <token>", "Content-Type": "application/json"}
+
+# Cookie-based authentication
+cookies = {"session": "session_value"}
+
+# Multiple methods
+resp = requests.request("DELETE", url, headers=headers)
+```
+
+## Test Categories
+
+### Vertical Privilege Escalation
+Test admin endpoints with regular user credentials:
+```python
+for endpoint in admin_endpoints:
+    resp = requests.get(url, headers=user_headers)
+    # 200 = VULNERABLE, 403 = properly restricted
+```
+
+### Horizontal Privilege Escalation (IDOR)
+Access other users' resources:
+```python
+# Replace {id} with other user's ID
+resp = requests.get(f"/api/users/{other_id}/profile", headers=user_headers)
+```
+
+### HTTP Method Override
+```python
+override_headers = ["X-HTTP-Method-Override", "X-Method-Override", "X-HTTP-Method"]
+```
+
+### Mass Assignment Fields
+| Field | Description |
+|-------|-------------|
+| `role` | User role (admin, user) |
+| `is_admin` | Boolean admin flag |
+| `permissions` | Permission array |
+| `access_level` | Numeric access level |
+| `user_type` | User type classification |
+
+## Response Status Interpretation
+| Status | Meaning |
+|--------|---------|
+| 200/201 | Access granted (potential vulnerability if unexpected) |
+| 401 | Not authenticated |
+| 403 | Authenticated but not authorized (correct behavior) |
+| 404 | Resource not found (may hide from unauthorized users) |
+| 405 | Method not allowed |
+
+## OWASP References
+- A01:2021 Broken Access Control: https://owasp.org/Top10/A01_2021-Broken_Access_Control/
+- WSTG Access Control: https://owasp.org/www-project-web-security-testing-guide/latest/4-Web_Application_Security_Testing/05-Authorization_Testing/
+- IDOR Testing: https://owasp.org/www-project-web-security-testing-guide/latest/4-Web_Application_Security_Testing/05-Authorization_Testing/04-Testing_for_Insecure_Direct_Object_References