fix(proxy,tooling): serialize+reconnect Caido client, actionable HTTPQL errors, sandbox tool guidance (#794)

* fix(proxy,tooling): serialize+reconnect Caido client, actionable HTTPQL errors, sandbox tool guidance

Addresses the top recurring agent tool-call failures observed in telemetry:

- proxy: the shared Caido client had no locking or reconnect, so concurrent
  agent calls raced ("Transport is already connected") and a dead transport
  poisoned the rest of the run ("Connector is closed"/"Server disconnected").
  Add an asyncio lock + bounded reconnect in caido_api.call_with_client (sandbox
  path) and a scan-wide caido_lock in the run context that host-side proxy tools
  hold around every call. Deterministic errors are not retried.
- proxy: list_requests now returns Caido's exact parser message, echoes the
  offending query, and includes a corrected-syntax hint so agents self-correct
  instead of retrying a broken HTTPQL filter.
- shell/prompt: document that write_stdin requires a process started with
  tty=true; nudge toward writing Python to a file over deeply-nested one-liners;
  note the venv pre-installs common libs.
- agent-browser: distinguish daemon/connection failures (run doctor, don't loop)
  from malformed commands; invoke directly (no sh -c wrapper).
- containers: use POSIX '.' instead of the bashism 'source' in generated rc
  files (fixes 'sh: source: not found'); add file + xxd and pre-install
  requests/httpx/beautifulsoup4/lxml/pyjwt/cryptography in the sandbox venv.
- tests: cover proxy serialization/reconnect/no-retry and HTTPQL errors.

* fix(proxy): host-side reconnect, close stale clients, don't retry mutations

Addresses Greptile review on the reconnect logic:

- Host path had no reconnect: a dead shared context client (Caido restart /
  network blip) previously disabled proxy tools for the rest of the scan. Add
  SharedCaidoClient, a serialized reconnect-safe holder stored once per scan in
  the run context and shared across agents. On a dead transport it rebuilds via
  reconnect_caido, which re-selects the SAME Caido project (preserving captured
  traffic) instead of creating a new empty one.
- Don't repeat completed mutations: call_with_client / SharedCaidoClient.call
  take idempotent=. Reads retry once on reconnect; replay + scope
  create/update/delete heal the client but re-raise instead of risking a
  double-apply.
- Don't leak replaced clients: the stale client is aclose()d (best-effort) on
  every reconnect.
- Extend tests to cover close-on-reconnect, non-idempotent re-raise, and the
  SharedCaidoClient holder.

* fix(proxy): close replacement Caido client when project.select fails

Addresses Greptile P1: in reconnect_caido (and bootstrap_caido) a successful
connect() followed by a failing project.select()/create() discarded the
connected client without closing it, so a missing/unavailable project could
leak a transport on every retry. Close the client before re-raising.

---------

Co-authored-by: Alex Schapiro <bearsyankees@gmail.com>

strix/skills/tooling/python.md

@@ -92,10 +92,18 @@ For iterative exploit work, put code in a file:
 
 ## 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):
+The sandbox's Python lives in `/app/.venv`, and it is the active virtualenv
+(`python3` / `pip` already resolve to it). The following common libraries are
+**pre-installed** — import them directly, no install step needed:
+`requests`, `httpx`, `beautifulsoup4` (`bs4`), `lxml`, `pyjwt` (`jwt`),
+`cryptography`.
+
+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>
 ```
+
+Plain `pip install <package>` also works because the venv is active. Install
+before you import, so scripts don't fail with `ModuleNotFoundError`.