Sign bundled macOS helper binaries (#35264)

## Why

The macOS release workflow fetched `rg` and zsh while assembling package
archives, after the signing stage. This left the bundled helper executables
outside the workflow's signing and notarization checks.

## What changed

- Fetch, sign, notarize, and upload the pinned macOS `rg` and zsh binaries with
  the other release artifacts.
- Build package archives from those signed helpers via `--rg-bin` and the new
  `--zsh-bin` override.
- Verify the helpers' architecture, signatures, and absence of entitlements in
  the final package.

## Testing

- Cover the prebuilt zsh override and verify that package assembly preserves
  the supplied helper binaries.

GitOrigin-RevId: a3865c04fa2f0f4df32e627ee7202bc87bdc3241

scripts/codex_package/cli.py

@@ -98,7 +98,8 @@ def parse_args() -> argparse.Namespace:
             "targets, bwrap is built with Cargo."
         ),
     )
-    parser.add_argument(
+    zsh_source = parser.add_mutually_exclusive_group()
+    zsh_source.add_argument(
         "--zsh-manifest",
         type=Path,
         help=(
@@ -106,6 +107,11 @@ def parse_args() -> argparse.Namespace:
             "scripts/codex_package/codex-zsh."
         ),
     )
+    zsh_source.add_argument(
+        "--zsh-bin",
+        type=Path,
+        help="Optional prebuilt zsh executable instead of fetching from a manifest.",
+    )
     parser.add_argument(
         "--codex-command-runner-bin",
         type=Path,
@@ -182,7 +188,7 @@ def main() -> int:
         entrypoint_bin=source_outputs.entrypoint_bin,
         code_mode_host_bin=source_outputs.code_mode_host_bin,
         rg_bin=resolve_rg_bin(spec, args.rg_bin),
-        zsh_bin=resolve_zsh_bin(spec, args.zsh_manifest),
+        zsh_bin=resolve_zsh_bin(spec, args.zsh_manifest, zsh_bin=args.zsh_bin),
         bwrap_bin=source_outputs.bwrap_bin,
         codex_command_runner_bin=source_outputs.codex_command_runner_bin,
         codex_windows_sandbox_setup_bin=source_outputs.codex_windows_sandbox_setup_bin,