dotslash: publish Codex entrypoints from package archives

## Summary

DotSlash should resolve the same canonical package layout used by standalone installers and npm platform packages, but it should not take the size regression of downloading gzip-compressed package archives. Installers continue to use `.tar.gz` because that format is broadly available, while DotSlash can use zstd-compressed tar archives.

This updates the package archive release helper to emit both `*.tar.gz` and `*.tar.zst` package archives from the same package directory. The Codex CLI and `codex-app-server` DotSlash release config entries now match `codex-package-<target>.tar.zst` and `codex-app-server-package-<target>.tar.zst`, with paths that select `bin/codex` or `bin/codex-app-server` inside the extracted package. The Windows release compression loop also skips prebuilt `.tar.zst` archives so it does not try to recompress them as ordinary files.

The other helper outputs stay on their existing per-binary artifacts for now.

## Test plan

- `python3 -m json.tool .github/dotslash-config.json > /dev/null`
- `bash -n .github/scripts/build-codex-package-archive.sh`
- `python3 -m py_compile scripts/codex_package/cli.py`
- `ruby -e 'require "yaml"; YAML.load_file(".github/workflows/rust-release-windows.yml"); puts "ok"'`
- Ran a Python regex smoke test that checked every updated `codex` and `codex-app-server` platform entry against the `.tar.zst` archive names emitted by `.github/scripts/build-codex-package-archive.sh`.
- Ran `scripts/build_codex_package.py` with synthetic macOS entrypoint and `rg` binaries and repeated `--archive-output` values for `.tar.gz` and `.tar.zst`, verifying both archives were written.

.github/workflows/rust-release-windows.yml

@@ -295,7 +295,7 @@ jobs:
             base="$(basename "$f")"
             # Skip files that are already archives (shouldn't happen, but be
             # safe).
-            if [[ "$base" == *.tar.gz || "$base" == *.zip || "$base" == *.dmg ]]; then
+            if [[ "$base" == *.tar.gz || "$base" == *.tar.zst || "$base" == *.zip || "$base" == *.dmg ]]; then
               continue
             fi