feat(provision): install pipelock CA into the agent + add curl

Second step of PRD 0006. With pipelock now doing the bumping, the
agent's TLS library has to trust pipelock's per-bottle CA — or
every CONNECT to api.anthropic.com is a self-signed-cert error.

- BottleBackend.provision gains a non-abstract `provision_ca`
  with a default no-op (so non-Docker backends aren't forced to
  implement TLS interception) and orchestrates
  ca → prompt → skills → ssh → git. CA install runs first so the
  agent's trust store is rebuilt before anything else in the
  agent makes a TLS call.

- New backend/docker/provision/ca.py: docker-cp's the CA cert
  into the agent at /usr/local/share/ca-certificates/...,
  `update-ca-certificates`, then emits a one-line stderr log
  with the SHA-256 fingerprint (stdlib `ssl` + `hashlib`; no
  subprocess for crypto). Module-level constants AGENT_CA_PATH
  and AGENT_CA_BUNDLE are imported by launch.py so the env
  trio set at docker run time matches the paths the provisioner
  writes.

- launch.py: rebinds `plan` after `dataclasses.replace`s on the
  pipelock proxy plan so provision_ca (which reads
  `plan.proxy_plan.ca_cert_host_path`) sees the populated CA
  paths. Three new -e flags on the agent's docker run for the
  NODE_EXTRA_CA_CERTS / SSL_CERT_FILE / REQUESTS_CA_BUNDLE trio.

- Dockerfile: adds curl to the apt-get install line. curl
  natively respects HTTPS_PROXY and sends CONNECT directly —
  the agent doesn't need OS-level DNS for external hostnames
  (pipelock resolves them on its side of the bumped tunnel).
  This is the "simple HTTPS request" path the earlier turn
  needed and Node's stdlib https.request couldn't provide.

Co-Authored-By: Claude Opus 4.7 <noreply@anthropic.com>

Dockerfile

@@ -19,9 +19,11 @@ FROM node:22-slim
 # clarity in case the base ever drops it. socat is the privileged
 # forwarder for the in-container ssh-agent (see claude_bottle/ssh.py): the agent
 # runs as root and rejects non-root connections, so socat sits between
-# node and the agent socket.
+# node and the agent socket. curl is here so any HTTPS_PROXY-aware
+# tool (curl itself, plus anything that shells out to it) works
+# against pipelock's bumped TLS without the agent needing local DNS.
 RUN apt-get update \
-  && apt-get install -y --no-install-recommends git ca-certificates openssh-client socat \
+  && apt-get install -y --no-install-recommends git ca-certificates openssh-client socat curl \
   && rm -rf /var/lib/apt/lists/*
 
 # Install claude-code globally. Pinned to the version verified in the v1