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/Dockerfile

@@ -88,10 +88,10 @@ RUN npm install -g retire@latest && \
     npm install -g tree-sitter-cli@latest && \
     npm install -g agent-browser@0.26.0
 
-USER pentester
 ENV AGENT_BROWSER_EXECUTABLE_PATH=/usr/bin/chromium
 ENV AGENT_BROWSER_USER_AGENT="Mozilla/5.0 (X11; Linux x86_64) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/131.0.0.0 Safari/537.36"
-ENV AGENT_BROWSER_ARGS="--disable-blink-features=AutomationControlled --exclude-switches=enable-automation --disable-features=IsolateOrigins,site-per-process,Translate,BlinkGenPropertyTrees --no-first-run --no-default-browser-check --window-size=1920,1080 --lang=en-US,en --disable-infobars --disable-notifications --disable-save-password-bubble --disable-session-crashed-bubble"
+ENV AGENT_BROWSER_ARGS="--disable-blink-features=AutomationControlled,--no-first-run,--no-default-browser-check,--lang=en-US"
+ENV AGENT_BROWSER_SCREENSHOT_DIR=/workspace/.agent-browser-screenshots
 RUN /home/pentester/.npm-global/bin/agent-browser doctor --offline --quick
 
 RUN set -eux; \