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-device-posture-assessment-in-zero-trust/references/api-reference.md

@@ -0,0 +1,53 @@
+# API Reference: Device Posture Assessment Agent
+
+## Dependencies
+
+| Library | Version | Purpose |
+|---------|---------|---------|
+| (stdlib only) | Python 3.8+ | Platform detection, subprocess for OS security checks |
+
+## CLI Usage
+
+```bash
+python scripts/agent.py --output-dir /reports/ --output device_posture.json
+```
+
+## Functions
+
+### `check_os_version() -> dict`
+Uses `platform.system()`, `platform.version()` for OS identification.
+
+### `check_disk_encryption() -> dict`
+Windows: `manage-bde -status C:` (BitLocker). macOS: `fdesetup status` (FileVault). Linux: `lsblk` for LUKS.
+
+### `check_firewall_status() -> dict`
+Windows: `netsh advfirewall show allprofiles state`. Linux: `ufw status`.
+
+### `check_antivirus() -> dict`
+Windows: PowerShell `Get-MpComputerStatus` for Defender real-time protection.
+
+### `check_screen_lock() -> dict`
+Windows: Registry `InactivityTimeoutSecs` check.
+
+### `compute_posture_score(checks) -> dict`
+Weighted scoring: encryption (25), firewall (20), AV (25), screen lock (15), OS (15). Returns COMPLIANT/PARTIAL/NON_COMPLIANT.
+
+## Posture Checks
+
+| Check | Weight | Tool |
+|-------|--------|------|
+| Disk Encryption | 25 | BitLocker/FileVault/LUKS |
+| Firewall | 20 | Windows Firewall/UFW |
+| Antivirus/EDR | 25 | Defender/endpoint agent |
+| Screen Lock | 15 | OS policy |
+| OS Supported | 15 | Platform detection |
+
+## Output Schema
+
+```json
+{
+  "hostname": "WORKSTATION-01",
+  "posture": {"score": 85, "compliance": "COMPLIANT"},
+  "recommendations": ["Enable disk encryption"]
+}
+```