build: fetch rg for Codex packages (#23526)

## Why

The Codex package builder should produce a complete package without
requiring callers to pre-populate `rg` under `codex-cli/vendor` or have
`dotslash` installed on `PATH`. The repo already tracks the
authoritative DotSlash manifest in `codex-cli/bin/rg`, so the builder
can read that metadata directly and fetch the correct ripgrep archive
for the target it is packaging.

## What changed

- Added `scripts/codex_package/ripgrep.py` to parse `codex-cli/bin/rg`
after stripping the shebang, select the target platform entry, download
the configured artifact, and verify the recorded size and SHA-256
digest.
- Added a cache under `$TMPDIR/codex-package/<target>-rg` so verified
archives can be reused without fetching again.
- Extracted `rg`/`rg.exe` from `tar.gz` and `zip` artifacts into the
package-builder cache, then copied that into `codex-path` through the
existing package layout flow.
- Kept `--rg-bin` as an explicit local override for offline tests and
unusual local workflows.
- Documented the default `rg` fetch/cache behavior in
`scripts/codex_package/README.md`.

## Verification

- Ran wrapper/module syntax compilation.
- Ran `scripts/build_codex_package.py --help` from `/private/tmp`.
- Ran a local manifest fetch test covering shebang-stripped manifest
parsing, `tar.gz` extraction, `zip` extraction, size/SHA-256
verification, and cache reuse after deleting the original source
archives.
- Ran fake-cargo package/archive builds for macOS, Linux, and Windows
target layouts with `--rg-bin`, including an assertion that generated
tar archives contain no duplicate member names.




---
[//]: # (BEGIN SAPLING FOOTER)
Stack created with [Sapling](https://sapling-scm.com). Best reviewed
with [ReviewStack](https://reviewstack.dev/openai/codex/pull/23526).
* #23541
* __->__ #23526

scripts/codex_package/ripgrep.py

@@ -0,0 +1,195 @@
+"""Fetch ripgrep from the DotSlash manifest used by the npm package."""
+
+import hashlib
+import json
+import shutil
+import stat
+import tarfile
+import tempfile
+import zipfile
+from dataclasses import dataclass
+from pathlib import Path
+from urllib.parse import urlparse
+from urllib.request import urlopen
+
+from .targets import REPO_ROOT
+from .targets import TargetSpec
+from .targets import resolve_input_path
+
+
+RG_MANIFEST = REPO_ROOT / "codex-cli" / "bin" / "rg"
+DOWNLOAD_TIMEOUT_SECS = 60
+
+
+@dataclass(frozen=True)
+class RgArtifact:
+    size: int
+    digest: str
+    archive_format: str
+    archive_member: str
+    url: str
+
+
+def resolve_rg_bin(spec: TargetSpec, rg_bin: Path | None) -> Path:
+    if rg_bin is not None:
+        return resolve_input_path(rg_bin, "ripgrep executable", "--rg-bin")
+
+    return fetch_rg(spec)
+
+
+def fetch_rg(
+    spec: TargetSpec,
+    *,
+    manifest_path: Path = RG_MANIFEST,
+    cache_root: Path | None = None,
+) -> Path:
+    artifact = artifact_for_target(spec, manifest_path)
+    cache_dir = (cache_root or default_cache_root()) / f"{spec.target}-rg"
+    archive_path = cache_dir / archive_filename(artifact.url)
+
+    if not archive_is_valid(archive_path, artifact):
+        download_archive(artifact.url, archive_path)
+        try:
+            verify_archive(archive_path, artifact)
+        except RuntimeError:
+            archive_path.unlink(missing_ok=True)
+            raise
+
+    dest = cache_dir / spec.rg_name
+    extract_rg(archive_path, artifact, dest)
+    if not spec.is_windows:
+        mode = dest.stat().st_mode
+        dest.chmod(mode | stat.S_IXUSR | stat.S_IXGRP | stat.S_IXOTH)
+    return dest
+
+
+def artifact_for_target(spec: TargetSpec, manifest_path: Path) -> RgArtifact:
+    manifest = load_manifest(manifest_path)
+    try:
+        platform_info = manifest["platforms"][spec.dotslash_platform]
+    except KeyError as exc:
+        raise RuntimeError(
+            f"ripgrep manifest {manifest_path} is missing platform {spec.dotslash_platform!r}"
+        ) from exc
+
+    providers = platform_info.get("providers")
+    if not providers:
+        raise RuntimeError(
+            f"ripgrep manifest {manifest_path} has no providers for {spec.dotslash_platform!r}"
+        )
+
+    hash_name = platform_info.get("hash")
+    if hash_name != "sha256":
+        raise RuntimeError(
+            f"Unsupported ripgrep hash {hash_name!r} for "
+            f"{spec.dotslash_platform!r}; expected sha256"
+        )
+
+    return RgArtifact(
+        size=int(platform_info["size"]),
+        digest=str(platform_info["digest"]),
+        archive_format=str(platform_info["format"]),
+        archive_member=str(platform_info["path"]),
+        url=str(providers[0]["url"]),
+    )
+
+
+def load_manifest(manifest_path: Path) -> dict:
+    text = manifest_path.read_text(encoding="utf-8")
+    if text.startswith("#!"):
+        text = "\n".join(text.splitlines()[1:])
+    return json.loads(text)
+
+
+def default_cache_root() -> Path:
+    return Path(tempfile.gettempdir()) / "codex-package"
+
+
+def archive_filename(url: str) -> str:
+    filename = Path(urlparse(url).path).name
+    if not filename:
+        raise RuntimeError(f"Unable to determine archive filename from {url}")
+    return filename
+
+
+def archive_is_valid(archive_path: Path, artifact: RgArtifact) -> bool:
+    if not archive_path.is_file():
+        return False
+    try:
+        verify_archive(archive_path, artifact)
+    except RuntimeError:
+        archive_path.unlink(missing_ok=True)
+        return False
+    return True
+
+
+def verify_archive(archive_path: Path, artifact: RgArtifact) -> None:
+    actual_size = archive_path.stat().st_size
+    if actual_size != artifact.size:
+        raise RuntimeError(
+            f"ripgrep archive {archive_path} has size {actual_size}, expected {artifact.size}"
+        )
+
+    digest = hashlib.sha256()
+    with open(archive_path, "rb") as fh:
+        for chunk in iter(lambda: fh.read(1024 * 1024), b""):
+            digest.update(chunk)
+
+    actual_digest = digest.hexdigest()
+    if actual_digest != artifact.digest:
+        raise RuntimeError(
+            f"ripgrep archive {archive_path} has sha256 {actual_digest}, "
+            f"expected {artifact.digest}"
+        )
+
+
+def download_archive(url: str, archive_path: Path) -> None:
+    archive_path.parent.mkdir(parents=True, exist_ok=True)
+    temp_path = archive_path.with_suffix(f"{archive_path.suffix}.tmp")
+    temp_path.unlink(missing_ok=True)
+    try:
+        with urlopen(url, timeout=DOWNLOAD_TIMEOUT_SECS) as response:
+            with open(temp_path, "wb") as out:
+                shutil.copyfileobj(response, out)
+        temp_path.replace(archive_path)
+    finally:
+        temp_path.unlink(missing_ok=True)
+
+
+def extract_rg(archive_path: Path, artifact: RgArtifact, dest: Path) -> None:
+    dest.parent.mkdir(parents=True, exist_ok=True)
+    dest.unlink(missing_ok=True)
+
+    if artifact.archive_format == "tar.gz":
+        with tarfile.open(archive_path, "r:gz") as archive:
+            try:
+                member = archive.getmember(artifact.archive_member)
+            except KeyError as exc:
+                raise RuntimeError(
+                    f"ripgrep archive {archive_path} is missing {artifact.archive_member!r}"
+                ) from exc
+
+            extracted = archive.extractfile(member)
+            if extracted is None:
+                raise RuntimeError(
+                    f"ripgrep archive member {artifact.archive_member!r} is not a file"
+                )
+            with extracted, open(dest, "wb") as out:
+                shutil.copyfileobj(extracted, out)
+        return
+
+    if artifact.archive_format == "zip":
+        with zipfile.ZipFile(archive_path) as archive:
+            try:
+                with archive.open(artifact.archive_member) as extracted:
+                    with open(dest, "wb") as out:
+                        shutil.copyfileobj(extracted, out)
+            except KeyError as exc:
+                raise RuntimeError(
+                    f"ripgrep archive {archive_path} is missing {artifact.archive_member!r}"
+                ) from exc
+        return
+
+    raise RuntimeError(
+        f"Unsupported ripgrep archive format {artifact.archive_format!r}; expected tar.gz or zip"
+    )