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-log-integrity-with-blockchain/SKILL.md

@@ -0,0 +1,33 @@
+---
+name: implementing-log-integrity-with-blockchain
+description: >-
+  Build an append-only log integrity chain using SHA-256 hash chaining for tamper detection.
+  Each log entry is hashed with the previous entry's hash to create a blockchain-like structure
+  where modifying any entry invalidates all subsequent hashes. Implements log ingestion,
+  chain verification, tamper detection with pinpoint identification, and periodic checkpoint
+  anchoring to external timestamping services.
+---
+
+## Instructions
+
+1. Install dependencies: `pip install requests`
+2. Ingest log entries from syslog, JSON, or plain text files.
+3. For each entry, compute SHA-256 hash of: previous_hash + timestamp + log_content.
+4. Store the chain as a JSON ledger with entry index, timestamp, content hash, previous hash, and chain hash.
+5. Verify chain integrity by recomputing all hashes and detecting breaks.
+6. Optionally anchor checkpoint hashes to an external timestamping service.
+
+```bash
+python scripts/agent.py --log-file /var/log/syslog --chain-file log_chain.json --verify --output integrity_report.json
+```
+
+## Examples
+
+### Chain Entry Structure
+```json
+{"index": 42, "timestamp": "2024-01-15T10:30:00Z", "content_hash": "a1b2c3...",
+ "prev_hash": "d4e5f6...", "chain_hash": "SHA256(prev_hash + timestamp + content_hash)"}
+```
+
+### Tamper Detection
+If entry 42 is modified, chain_hash[42] will not match SHA256(chain_hash[41] + ...), and all entries from 42 onward will be flagged as invalid.