chore: introduce publishing logic for @openai/codex-sdk (#4543)

There was a bit of copypasta I put up with when were publishing two
packages to npm, but now that it's three, I created some more scripts to
consolidate things.

With this change, I ran:

```shell
./scripts/stage_npm_packages.py --release-version 0.43.0-alpha.8 --package codex --package codex-responses-api-proxy --package codex-sdk
```

Indeed when it finished, I ended up with:

```shell
$ tree dist
dist
└── npm
    ├── codex-npm-0.43.0-alpha.8.tgz
    ├── codex-responses-api-proxy-npm-0.43.0-alpha.8.tgz
    └── codex-sdk-npm-0.43.0-alpha.8.tgz
$ tar tzvf dist/npm/codex-sdk-npm-0.43.0-alpha.8.tgz
-rwxr-xr-x  0 0      0    25476720 Oct 26  1985 package/vendor/aarch64-apple-darwin/codex/codex
-rwxr-xr-x  0 0      0    29871400 Oct 26  1985 package/vendor/aarch64-unknown-linux-musl/codex/codex
-rwxr-xr-x  0 0      0    28368096 Oct 26  1985 package/vendor/x86_64-apple-darwin/codex/codex
-rwxr-xr-x  0 0      0    36029472 Oct 26  1985 package/vendor/x86_64-unknown-linux-musl/codex/codex
-rw-r--r--  0 0      0       10926 Oct 26  1985 package/LICENSE
-rw-r--r--  0 0      0    30187520 Oct 26  1985 package/vendor/aarch64-pc-windows-msvc/codex/codex.exe
-rw-r--r--  0 0      0    35277824 Oct 26  1985 package/vendor/x86_64-pc-windows-msvc/codex/codex.exe
-rw-r--r--  0 0      0        4842 Oct 26  1985 package/dist/index.js
-rw-r--r--  0 0      0        1347 Oct 26  1985 package/package.json
-rw-r--r--  0 0      0        9867 Oct 26  1985 package/dist/index.js.map
-rw-r--r--  0 0      0          12 Oct 26  1985 package/README.md
-rw-r--r--  0 0      0        4287 Oct 26  1985 package/dist/index.d.ts
```

.github/workflows/ci.yml

@@ -27,7 +27,7 @@ jobs:
       - name: Install dependencies
         run: pnpm install --frozen-lockfile
 
-      # build_npm_package.py requires DotSlash when staging releases.
+      # stage_npm_packages.py requires DotSlash when staging releases.
       - uses: facebook/install-dotslash@v2
 
       - name: Stage npm package
@@ -37,10 +37,12 @@ jobs:
         run: |
           set -euo pipefail
           CODEX_VERSION=0.40.0
-          PACK_OUTPUT="${RUNNER_TEMP}/codex-npm.tgz"
-          python3 ./codex-cli/scripts/build_npm_package.py \
+          OUTPUT_DIR="${RUNNER_TEMP}"
+          python3 ./scripts/stage_npm_packages.py \
             --release-version "$CODEX_VERSION" \
-            --pack-output "$PACK_OUTPUT"
+            --package codex \
+            --output-dir "$OUTPUT_DIR"
+          PACK_OUTPUT="${OUTPUT_DIR}/codex-npm-${CODEX_VERSION}.tgz"
           echo "pack_output=$PACK_OUTPUT" >> "$GITHUB_OUTPUT"
 
       - name: Upload staged npm package artifact