fix(cron_vm): greptile — portable uv arch + keep master key out of /proc/cmdline

- Replace the hardcoded `x86_64-unknown-linux-gnu` triple in the uv
  tarball download with `$(uname -m)`-unknown-linux-gnu so the same
  script also works on aarch64 hosts. Astral publishes both triples
  under the same release tag and uname -m already returns the exact
  token uv uses.

- Move LITELLM_MASTER_KEY off the setsid argv (`setsid env KEY=VAL
  bash ...`) and onto a shell-prefix assignment on setsid. The argv
  form puts the literal key in /proc/<setsid-pid>/cmdline where a
  local reader (model-directed Read tool, other VM users, crash dump)
  could pick it up before exec into the litellm child. The prefix
  form keeps the key out of argv at every layer (setsid → bash → uv
  → litellm).

tests/claude_code/cron_vm/run_daily.sh

@@ -268,7 +268,13 @@ else
   if [[ ! -x "${WORKTREE_UV}" ]]; then
     log "downloading uv ${PINNED_UV_VERSION} for the worktree"
     mkdir -p "${WORKTREE}/.uv-bin"
-    UV_TARBALL_NAME="uv-x86_64-unknown-linux-gnu.tar.gz"
+    # Detect host arch so the same script works on x86_64 GCP VMs and on
+    # aarch64 hosts (Astral publishes both `uv-x86_64-unknown-linux-gnu`
+    # and `uv-aarch64-unknown-linux-gnu` tarballs under the same release
+    # tag, and `uname -m` already returns the exact token uv uses).
+    UV_ARCH="$(uname -m)"
+    UV_TRIPLE="uv-${UV_ARCH}-unknown-linux-gnu"
+    UV_TARBALL_NAME="${UV_TRIPLE}.tar.gz"
     UV_DOWNLOAD_URL="https://github.com/astral-sh/uv/releases/download/${PINNED_UV_VERSION}/${UV_TARBALL_NAME}"
     UV_TMPDIR="$(mktemp -d -t uv-download.XXXXXX)"
     # Download the tarball and Astral's official .sha256 sidecar to disk
@@ -280,8 +286,8 @@ else
     curl -fsSL --output "${UV_TMPDIR}/${UV_TARBALL_NAME}.sha256" "${UV_DOWNLOAD_URL}.sha256"
     (cd "${UV_TMPDIR}" && sha256sum -c "${UV_TARBALL_NAME}.sha256") \
       || { rm -rf "${UV_TMPDIR}"; die "uv ${PINNED_UV_VERSION} sha256 mismatch — refusing to install"; }
-    tar -xzf "${UV_TMPDIR}/${UV_TARBALL_NAME}" -C "${UV_TMPDIR}" "uv-x86_64-unknown-linux-gnu/uv"
-    mv "${UV_TMPDIR}/uv-x86_64-unknown-linux-gnu/uv" "${WORKTREE_UV}.tmp"
+    tar -xzf "${UV_TMPDIR}/${UV_TARBALL_NAME}" -C "${UV_TMPDIR}" "${UV_TRIPLE}/uv"
+    mv "${UV_TMPDIR}/${UV_TRIPLE}/uv" "${WORKTREE_UV}.tmp"
     chmod +x "${WORKTREE_UV}.tmp"
     mv "${WORKTREE_UV}.tmp" "${WORKTREE_UV}"
     rm -rf "${UV_TMPDIR}"
@@ -314,7 +320,15 @@ log "starting proxy on 127.0.0.1:${PROXY_PORT}"
 # SIGTERM the whole tree by passing the pgid as a negative pid. We
 # write that pid to a file so cleanup() doesn't need to remember a
 # variable that might be stale by the time the trap fires.
-setsid env LITELLM_MASTER_KEY="${PROXY_API_KEY}" bash -c '
+#
+# Pass the master key as a shell-prefix assignment on `setsid` (inherited
+# via the environment) rather than as `env KEY=VAL ...` argv. The argv
+# form would land the literal key in /proc/<setsid-pid>/cmdline, where
+# any local reader (a model-directed `Read` tool call, another user on
+# the VM, a crash dump) could pick it up before the process execs into
+# the litellm child. The shell-prefix form keeps the key out of argv at
+# every layer (setsid → bash → uv → litellm).
+LITELLM_MASTER_KEY="${PROXY_API_KEY}" setsid bash -c '
   echo "$$" > "$0"
   cd "$1"
   exec "$2" run litellm --config "$3" --host 127.0.0.1 --port "$4"