fix(pipelock): write yaml to /etc/pipelock.yaml since image lacks /etc/pipelock

The pipelock image is distroless and does not contain /etc/pipelock/, so
docker cp to /etc/pipelock/pipelock.yaml fails with "Could not find the
file /etc/pipelock in container" — docker cp does not create missing
intermediate parent directories when targeting a stopped container, and
no shell is available in the image for a mkdir shim. Move the config
file to /etc/pipelock.yaml (directly under /etc, which always exists)
and update the --config argv to match. Also surface docker cp stderr in
the die message so future failures of this sort are debuggable.

Assisted-by: Claude Code

lib/pipelock.sh

@@ -271,7 +271,7 @@ pipelock_write_yaml() {
 #      service name. The image runs `pipelock` as its CMD; we override
 #      with `run --config <path>` and the listen address.
 #   2. `docker cp` the YAML config from the host mktemp dir into the
-#      container at /etc/pipelock/pipelock.yaml.
+#      container at /etc/pipelock.yaml.
 #
 # We use docker cp rather than `-v <host>:<container>` because Docker
 # Desktop bind mounts have ownership / case-sensitivity quirks on
@@ -308,29 +308,15 @@ pipelock_start() {
     die "pipelock yaml not found at ${host_yaml}; pipelock_write_yaml must run first"
   fi
 
-  # Container layout: pipelock reads its config from /etc/pipelock/pipelock.yaml.
-  # We bring the container up with a `sleep` shim so we can `docker cp`
-  # the config in, then restart with the real command — this avoids a
-  # bind mount entirely and keeps the host file off the container's
-  # filesystem after the cp completes.
-  #
-  # Two-phase boot:
-  #   phase 1: `docker run -d --entrypoint sh ... -c 'mkdir -p /etc/pipelock && sleep infinity'`
-  #            so we can cp the YAML in before pipelock starts and
-  #            tries to read it. We do NOT attach to internal_network
-  #            here; we'll connect after the config is in place so the
-  #            real pipelock process never sees a half-configured
-  #            agent on the wire.
-  #   phase 2: docker cp + docker restart with the real command via
-  #            --entrypoint reset (handled below).
+  # Container layout: pipelock reads its config from /etc/pipelock.yaml.
+  # We `docker create` the sidecar, `docker cp` the YAML into the
+  # writable layer, then `docker start` it — no bind mount, no shell
+  # shim. The image is distroless (no `sh`), and `docker cp` to a
+  # stopped container does NOT create intermediate parent directories,
+  # so the YAML lives directly under /etc rather than in a /etc/pipelock
+  # subdirectory.
   info "starting pipelock sidecar ${name} on network ${internal_network}"
 
-  # We cannot easily restart a container with a different command
-  # using `docker restart`. Instead, run the container in two stages:
-  # boot it with `sh -c 'mkdir + sleep'`, cp the file in, then start
-  # the real pipelock by docker exec'ing it as PID-N. A simpler
-  # approach: `docker create` + `docker cp` + `docker start`. Use that.
-  #
   # Sidecar argv verification (PR #1 review). The pinned digest
   # (CLAUDE_BOTTLE_PIPELOCK_IMAGE above) has:
   #   ENTRYPOINT ["/pipelock"]
@@ -348,18 +334,23 @@ pipelock_start() {
       --name "$name" \
       --network "$internal_network" \
       "$CLAUDE_BOTTLE_PIPELOCK_IMAGE" \
-      run --config /etc/pipelock/pipelock.yaml --listen "0.0.0.0:${CLAUDE_BOTTLE_PIPELOCK_PORT}" \
+      run --config /etc/pipelock.yaml --listen "0.0.0.0:${CLAUDE_BOTTLE_PIPELOCK_PORT}" \
       >/dev/null 2>&1; then
     die "failed to create pipelock sidecar ${name}"
   fi
 
-  # `docker cp` to a created-but-not-started container creates parent
-  # dirs as needed and works without the container running, since the
-  # cp is done against the writable layer directly.
-  if ! docker cp "$host_yaml" "${name}:/etc/pipelock/pipelock.yaml" >/dev/null 2>&1; then
+  # `docker cp` to a created-but-not-started container writes into the
+  # writable layer directly. The parent directory must already exist in
+  # the image — docker cp does NOT create missing intermediate dirs to
+  # a stopped container, contrary to a common assumption. The pipelock
+  # image is distroless (no `sh`), so we cannot prepopulate dirs with a
+  # shell shim either. We therefore put the config in /etc/pipelock.yaml
+  # (file directly under /etc) rather than /etc/pipelock/pipelock.yaml.
+  local cp_err
+  cp_err="$(docker cp "$host_yaml" "${name}:/etc/pipelock.yaml" 2>&1)" || {
     docker rm -f "$name" >/dev/null 2>&1 || true
-    die "failed to copy pipelock yaml into ${name}"
-  fi
+    die "failed to copy pipelock yaml into ${name}: ${cp_err}"
+  }
 
   # Attach to a per-agent user-defined bridge network for upstream
   # egress. The internal network has no gateway by definition, so