[codex] reuse release artifacts for npm staging (#27312)

The release job already downloads every workflow artifact into `dist`,
but npm staging creates a new cache and downloads the six target
artifacts again.

Reuse `dist` as the staging script's artifact cache while preserving the
existing download fallback for missing artifacts and standalone callers.
The script retains ownership of temporary caches but does not delete a
caller-provided directory.

In https://github.com/openai/codex/actions/runs/27242495616, the
duplicate
download transferred 3.3 GiB and took 4 minutes 13 seconds. This should
reduce total release time by about 4 minutes.

.github/workflows/rust-release.yml

@@ -1204,6 +1204,7 @@ jobs:
           ./scripts/stage_npm_packages.py \
             --release-version "$RELEASE_VERSION" \
             --workflow-url "$workflow_url" \
+            --artifacts-dir "${GITHUB_WORKSPACE}/dist" \
             --package codex \
             --package codex-responses-api-proxy \
             --package codex-sdk