Surface the previously-undocumented sandbox tools and unbreak two of them

The image ships 15 tools (jwt_tool, interactsh-client, arjun, dirsearch,
gospider, wafw00f, retire, eslint, jshint, js-beautify, JS-Snooper,
jsniper.sh, vulnx, ncat, uv) that the always-loaded skills never name
with usage guidance — agents could discover them via the environment
catalog but had no when/how. Add concise mentions in the natural home
for each: jwt_tool in the JWT skill, interactsh-client in the OAST
sections of SSRF/XXE/RCE, arjun in IDOR recon, dirsearch as the broad
alternate in the ffuf skill, gospider + the JS scrapers in katana,
wafw00f next to httpx, retire/eslint/jshint/js-beautify as a new
JavaScript-Side Coverage block in the SAST playbook, uv in python,
vulnx in the deep scan-mode CVE bullet, ncat in a new RCE Tooling
block.

Audit also turned up three real breakages along the way:

- jwt_tool's shebang resolves to /usr/bin/python3 but its dependencies
  live in /app/.venv, so every invocation died with
  ModuleNotFoundError: ratelimit. Replace the bare symlink with a
  wrapper that execs /app/.venv/bin/python against the real script.
- dirsearch's pipx venv ended up with setuptools 82, which dropped
  pkg_resources — startup failed before parsing args. Pin the inject
  to setuptools<81.
- ESLint's --no-eslintrc flag was removed in v9; the surviving
  --no-config-lookup covers it. Drop the dead flag from the SAST
  command block.

Also corrected the JS-Snooper / jsniper.sh entry in katana.md — both
take a bare domain and run their own JS discovery internally, not the
JS URLs Katana already harvested.

strix/skills/tooling/python.md

@@ -88,3 +88,13 @@ For iterative exploit work, put code in a file:
 2. Run it with `exec_command`: `python3 /workspace/scratch/exploit.py`.
 3. Edit and rerun until the proof-of-concept is reliable.
 ```
+
+## Installing extra packages
+
+The sandbox's Python lives in `/app/.venv`. To add a one-off dependency
+for an exploit script, use `uv` (already in the image and much faster
+than pip):
+
+```bash
+uv pip install --python /app/.venv/bin/python <package>
+```