Stabilize agent-browser launch and screenshot routing

AGENT_BROWSER_ARGS parser splits on commas, so any flag value
containing one (--disable-features=A,B, --window-size=1920,1080,
--lang=en-US,en) shredded into garbage positionals and Chromium
rejected the launch with "Multiple targets are not supported in
headless mode". Reduce to a comma-separated list of comma-free
flags that keeps the AutomationControlled anti-detection bit.

Default screenshot path now resolves inside the workspace root so
view_image accepts it; entrypoint pre-creates the dir at runtime
(the build-time mkdir is shadowed by the /workspace mount). Skill
examples updated to favor the no-arg form, plus brief fallback
guidance when view_image is unavailable on text-only models and a
viewport-resize note for sites that gate on real desktop dims.

Also drop the stale STRIX_DISABLE_BROWSER doc entry — no code
reference exists.

containers/docker-entrypoint.sh

@@ -90,6 +90,8 @@ sudo -u pentester certutil -N -d sql:/home/pentester/.pki/nssdb --empty-password
 sudo -u pentester certutil -A -n "Testing Root CA" -t "C,," -i /app/certs/ca.crt -d sql:/home/pentester/.pki/nssdb
 echo "✅ CA added to browser trust store"
 
+mkdir -p /workspace/.agent-browser-screenshots
+
 echo "✅ Container ready"
 
 cd /workspace