feat(tools): python_action — stateless Python execution with proxy helpers

Restores the legacy persistent-IPython tool's *ergonomics* (proxy
helpers pre-bound, structured stdout/stderr/error returns) without the
in-container daemon: each call ships ``strix.tools.proxy._calls`` source
into ``/tmp`` alongside a per-call driver, runs ``python3 -u`` against
it, and parses a sentinel-delimited JSON payload back from stdout. The
driver fetches its own guest token from Caido at ``localhost:48080``
and binds ``list_requests`` / ``view_request`` / ``send_request`` /
``repeat_request`` / ``scope_rules`` to that client; user code runs
inside an ``async def`` wrapper so top-level ``await`` works.

The proxy SDK call sequences live in one file —
``strix/tools/proxy/_calls.py`` — and are reused by both the host-side
``@function_tool`` wrappers (which add JSON serialization for the LLM)
and the in-container kernel (which exposes the bare async functions).
No code duplication; the helper logic itself is host-shipped, so
tweaking the proxy helpers does not require an image rebuild.

Image: a single ``pip install caido-sdk-client`` line so the driver's
``import caido_sdk_client`` resolves. Skill ``tooling/python`` is
always-loaded alongside ``tooling/agent_browser``.

Trade-off accepted: state does not persist across calls (no kernel).
For multi-step workflows the agent combines into one ``code`` block or
writes a script to ``/workspace/scratch/`` and runs via
``exec_command``. If a workflow surfaces that genuinely needs
persistence, the same tool surface migrates to a kernel-backed
executor without changing the LLM contract.

Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>

containers/Dockerfile

@@ -77,6 +77,13 @@ RUN pipx install arjun && \
     pipx inject dirsearch setuptools && \
     pipx install wafw00f
 
+# ``python_action`` ships a fresh ``caido-sdk-client`` per call into /tmp.
+# Install it system-wide so the driver's ``import caido_sdk_client`` resolves
+# without venv activation. The helper *logic* lives host-side in
+# ``strix/tools/proxy/_calls.py`` (shipped at runtime) — only the SDK dep
+# is image-baked.
+RUN pip install --break-system-packages --no-cache-dir caido-sdk-client
+
 ENV NPM_CONFIG_PREFIX=/home/pentester/.npm-global
 RUN mkdir -p /home/pentester/.npm-global