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/implementing-passwordless-auth-with-microsoft-entra/references/api-reference.md

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+# API Reference: Implementing Passwordless Auth with Microsoft Entra
+
+## Libraries
+
+### msal (Microsoft Authentication Library)
+- **Install**: `pip install msal`
+- **Docs**: https://msal-python.readthedocs.io/
+- `ConfidentialClientApplication()` -- App registration auth
+- `acquire_token_for_client()` -- Client credentials flow
+
+### Microsoft Graph API
+- **Base**: `https://graph.microsoft.com/v1.0` and `/beta`
+- **Docs**: https://learn.microsoft.com/en-us/graph/api/overview
+
+## Authentication Methods Policy API
+
+| Endpoint | Description |
+|----------|-------------|
+| `GET /policies/authenticationMethodsPolicy` | Full auth methods config |
+| `GET /users/{id}/authentication/methods` | User's registered methods |
+| `GET /users/{id}/authentication/fido2Methods` | FIDO2 keys for user |
+| `GET /users/{id}/authentication/microsoftAuthenticatorMethods` | Authenticator setup |
+| `GET /users/{id}/authentication/windowsHelloForBusinessMethods` | WHfB status |
+
+## Conditional Access API
+
+| Endpoint | Description |
+|----------|-------------|
+| `GET /identity/conditionalAccess/policies` | List CA policies |
+| `GET /identity/conditionalAccess/authenticationStrength/policies` | Auth strength policies |
+
+## Sign-In Logs API
+
+| Endpoint | Description |
+|----------|-------------|
+| `GET /auditLogs/signIns` | Sign-in activity logs |
+| Filter: `authenticationDetails/any(a:a/authenticationMethod eq 'FIDO2 security key')` |
+
+## Authentication Method Types
+- `fido2AuthenticationMethod` -- FIDO2 security keys
+- `microsoftAuthenticatorAuthenticationMethod` -- Authenticator app
+- `windowsHelloForBusinessAuthenticationMethod` -- Windows Hello
+- `passwordAuthenticationMethod` -- Traditional password
+- `phoneAuthenticationMethod` -- SMS/phone call (legacy)
+- `emailAuthenticationMethod` -- Email OTP
+
+## Required Graph Permissions
+- `UserAuthenticationMethod.Read.All`
+- `Policy.Read.All`
+- `AuditLog.Read.All`
+- `User.Read.All`
+
+## External References
+- Entra Passwordless: https://learn.microsoft.com/en-us/entra/identity/authentication/concept-authentication-passwordless
+- FIDO2 Keys: https://learn.microsoft.com/en-us/entra/identity/authentication/howto-authentication-passwordless-security-key
+- Graph Auth Methods: https://learn.microsoft.com/en-us/graph/api/resources/authenticationmethods-overview
+- Conditional Access Auth Strength: https://learn.microsoft.com/en-us/entra/identity/authentication/concept-authentication-strengths