npm: ship platform packages in Codex package layout

## Summary

The npm platform packages should stop carrying a bespoke native layout now that the release workflow builds canonical Codex package archives. Keeping npm on the same `bin/`, `codex-resources/`, and `codex-path/` structure lets the Rust package-layout detection behave consistently across standalone, npm, and future DotSlash installs.

This changes platform npm packages to stage the `codex-package` artifact for each target under `vendor/<target>`. The Node launcher now resolves `bin/codex` and prepends `codex-path`, while retaining legacy `vendor/<target>/codex` and `vendor/<target>/path` fallback support for local development and migration. The npm staging helper downloads `codex-package` archives instead of rebuilding the CLI payload from individual `codex`, `rg`, `bwrap`, and sandbox helper artifacts.

CI still needs to stage npm packages from historical rust-release workflow artifacts that predate package archives, so the staging scripts now expose an explicit `--allow-legacy-codex-package` fallback. That fallback synthesizes the canonical package layout from legacy per-binary artifacts and is wired only into the CI smoke path; release staging remains strict and continues to require real package archives.

## Test plan

- `python3 -m py_compile codex-cli/scripts/build_npm_package.py codex-cli/scripts/install_native_deps.py scripts/stage_npm_packages.py scripts/codex_package/cli.py`
- `node --check codex-cli/bin/codex.js`
- `ruby -e 'require "yaml"; YAML.load_file(".github/workflows/rust-release.yml"); YAML.load_file(".github/workflows/ci.yml"); puts "ok"'`
- Staged a synthetic `codex-linux-x64` platform package from a canonical vendor tree and verified it copied only `bin/`, `codex-path/`, `codex-resources/`, and `codex-package.json`.
- Imported `install_native_deps.py` and extracted a synthetic `codex-package-x86_64-unknown-linux-musl.tar.gz` into `vendor/<target>`.
- Ran legacy-layout conversion smokes for Linux, Windows, and unsigned macOS artifact naming.
- `NPM_CONFIG_CACHE="$tmp_dir/npm-cache" python3 ./scripts/stage_npm_packages.py --release-version 0.125.0 --workflow-url https://github.com/openai/codex/actions/runs/26131514935 --package codex --allow-legacy-codex-package --output-dir "$tmp_dir"`
- `node codex-cli/bin/codex.js --version`

.github/workflows/ci.yml

@@ -53,14 +53,16 @@ jobs:
           # Passing the workflow URL directly avoids relying on old rust-v*
           # branches remaining discoverable via `gh run list --branch ...`.
           CODEX_VERSION=0.125.0
-          WORKFLOW_URL="https://github.com/openai/codex/actions/runs/24901475298"
+          WORKFLOW_URL="https://github.com/openai/codex/actions/runs/26131514935"
           OUTPUT_DIR="${RUNNER_TEMP}"
-          # This reused workflow predates the standalone bwrap artifact.
+          # This reused workflow predates codex-package archive artifacts, so
+          # CI synthesizes the package layout from the older per-binary
+          # artifacts. Release staging must use real package archives.
           python3 ./scripts/stage_npm_packages.py \
             --release-version "$CODEX_VERSION" \
             --workflow-url "$WORKFLOW_URL" \
             --package codex \
-            --allow-missing-native-component bwrap \
+            --allow-legacy-codex-package \
             --output-dir "$OUTPUT_DIR"
           PACK_OUTPUT="${OUTPUT_DIR}/codex-npm-${CODEX_VERSION}.tgz"
           echo "pack_output=$PACK_OUTPUT" >> "$GITHUB_OUTPUT"

.github/workflows/rust-release.yml

@@ -1208,8 +1208,6 @@ jobs:
         if: ${{ env.SIGN_MACOS == 'true' }}
         run: pnpm install --frozen-lockfile
 
-      # stage_npm_packages.py requires DotSlash when staging releases.
-      - uses: facebook/install-dotslash@1e4e7b3e07eaca387acb98f1d4720e0bee8dbb6a # v2
       - name: Stage npm packages
         if: ${{ env.SIGN_MACOS == 'true' }}
         env: