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>

pyproject.toml

@@ -227,6 +227,9 @@ ignore = [
 "strix/tools/thinking/tool.py" = ["TC002"]
 "strix/tools/web_search/tool.py" = ["TC002"]
 "strix/tools/proxy/tools.py" = ["TC002", "PLR0911"]
+# Driver script writes to /tmp inside the sandbox container — single-user,
+# isolated rootfs, so the multi-user race S108 warns about doesn't apply.
+"strix/tools/python/tool.py" = ["S108", "TC002"]
 "strix/tools/agents_graph/tools.py" = ["TC002"]
 "strix/agents/factory.py" = ["TC002"]
 # Entry point: ``Path`` is used at runtime by the typing of the