Production hardening: security fixes, code quality, 724 skills complete

- Fix 25 shell=True subprocess calls with list-based commands
- Fix 49 verify=False in defensive skills (env-var override)
- Add timeout to 231 HTTP/subprocess/socket calls
- Fix 6 SQL injection patterns with whitelist validation
- Replace 8 __import__() with standard imports
- Remove 701 unused imports across 442 files
- Add authorized-testing disclaimers to all offensive skills
- Complete 11 incomplete skill directories
- Expand 10 stub SKILL.md files with full content
- Fix 2 YAML parse errors in frontmatter
- Fix 5 pre-existing syntax errors
- Convert 22 hardcoded paths/ports to environment variables
- Back up 21 redundant skill pairs to .bak
- Fix 2 global declaration errors
- 724/724 skills with full folder anatomy (SKILL.md + agent.py + api-reference.md + LICENSE)
- 0 compile errors across all 724 agent.py files

skills/scanning-infrastructure-with-nessus/scripts/agent.py

@@ -7,6 +7,7 @@ vulnerability reports with severity-based prioritization.
 """
 
 import json
+import os
 import sys
 import time
 import urllib3
@@ -24,9 +25,9 @@ urllib3.disable_warnings(urllib3.exceptions.InsecureRequestWarning)
 class NessusScanAgent:
     """Manages Nessus vulnerability scans via REST API."""
 
-    def __init__(self, host="https://localhost:8834", username="admin",
+    def __init__(self, host=None, username="admin",
                  password="", output_dir="./nessus_scan"):
-        self.base_url = host.rstrip("/")
+        self.base_url = (host or os.environ.get("NESSUS_URL", "https://localhost:8834")).rstrip("/")
         self.username = username
         self.password = password
         self.token = None