npm: remove legacy package artifact synthesis (#23836)

## Why

`rust-release` now publishes `codex-package-<target>.tar.gz` as the
canonical native package payload. npm staging should consume those
archives directly instead of keeping legacy synthesis code that fetched
`rg`, copied standalone binaries, and rebuilt an approximate package
layout.

That also means the package builder should not know the internal shape
of `codex-package`. It should extract and copy the target payload
wholesale so future layout changes stay localized to the archive
producer.

The release job stages `codex`, `codex-responses-api-proxy`, and
`codex-sdk` together, so native artifact download should be filtered,
observable, and shared across component installs. Since that native
hydration is now only used by release staging, keeping a separate
`install_native_deps.py` CLI adds an extra wrapper without a real
caller.

## What Changed

- Removed legacy `codex-package` synthesis and related compatibility
flags from npm staging.
- Folded the remaining native artifact hydration code into
`scripts/stage_npm_packages.py` and deleted
`codex-cli/scripts/install_native_deps.py`.
- Made platform package staging copy the full extracted target directory
instead of enumerating package entries.
- Kept non-`codex-package` native components under their component
directory name instead of using a legacy destination map.
- Split native staging by component set while sharing one
workflow-artifact cache across the invocation.
- Changed workflow artifact download to select target artifacts by name,
print sizes/progress, and reuse cached artifacts.
- Removed the implicit `CI=true` default from `build_npm_package.py`;
local CI-shaped runs should set that environment explicitly.
- Kept `npm pack` cache/log output in its temporary directory so packing
does not write to the user npm cache.

## Verification

- `python3 -m py_compile scripts/stage_npm_packages.py
codex-cli/scripts/build_npm_package.py`
- `python3 -m unittest discover -s scripts/codex_package -p "test_*.py"`
- `scripts/stage_npm_packages.py --help`
- `codex-cli/scripts/build_npm_package.py --help`
- Ran the release-shaped staging command from `rust-release.yml` against
workflow run https://github.com/openai/codex/actions/runs/26240748758
with `CI=true` set locally to match GitHub Actions:

```sh
CI=true python3 ./scripts/stage_npm_packages.py \
  --release-version 0.133.0 \
  --workflow-url https://github.com/openai/codex/actions/runs/26240748758 \
  --package codex \
  --package codex-responses-api-proxy \
  --package codex-sdk
```

That completed successfully, downloaded only the six target artifacts
once, reused the cache for `codex-responses-api-proxy`, and produced all
nine npm tarballs. Generated tarballs and staging/artifact temp dirs
were cleaned afterward.

.github/workflows/ci.yml

@@ -42,9 +42,6 @@ jobs:
       - name: Install dependencies
         run: pnpm install --frozen-lockfile
 
-      # stage_npm_packages.py requires DotSlash when staging releases.
-      - uses: facebook/install-dotslash@1e4e7b3e07eaca387acb98f1d4720e0bee8dbb6a # v2
-
       - name: Stage npm package
         id: stage_npm_package
         env:
@@ -55,17 +52,13 @@ jobs:
           # cross-platform native payload required by the npm package layout.
           # 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/26131514935"
+          CODEX_VERSION=0.133.0-alpha.4
+          WORKFLOW_URL="https://github.com/openai/codex/actions/runs/26201494185"
           OUTPUT_DIR="${RUNNER_TEMP}"
-          # This reused workflow predates codex-package archive artifacts, so
-          # CI synthesizes the package layout from the older per-binary
-          # artifacts. Release staging must use real package archives.
           python3 ./scripts/stage_npm_packages.py \
             --release-version "$CODEX_VERSION" \
             --workflow-url "$WORKFLOW_URL" \
             --package codex \
-            --allow-legacy-codex-package \
             --output-dir "$OUTPUT_DIR"
           PACK_OUTPUT="${OUTPUT_DIR}/codex-npm-${CODEX_VERSION}.tgz"
           echo "pack_output=$PACK_OUTPUT" >> "$GITHUB_OUTPUT"