[codex] Revert shared BuildBuddy Bazel wrapper (#25909)

## Why

PR #25905 intentionally adds a failing `codex-core` unit test, but its
[Bazel test on Windows
check](https://github.com/openai/codex/actions/runs/26837526950/job/79135369259)
passed. That shows the Bazel configuration introduced by #25156 is not
behaving as expected, so revert it while the configuration can be
investigated separately.

## What changed

Revert #25156 in full, restoring the previous Bazel remote
configuration, CI scripts, workflows, `rusty_v8` handling, and
documentation. This removes the shared BuildBuddy wrapper and its tests.

## Validation

Not run locally; this exact revert was prioritized for a fast rollback.

.github/scripts/test_rusty_v8_bazel.py

@@ -88,49 +88,24 @@ class RustyV8BazelTest(unittest.TestCase):
             ),
         )
 
-    def test_bazel_commands_use_shared_buildbuddy_remote_config_library(self) -> None:
-        with patch.dict(environ, {}, clear=True):
+    def test_bazel_remote_args_include_buildbuddy_header_when_present(self) -> None:
+        with patch.dict(environ, {"BUILDBUDDY_API_KEY": "token"}, clear=False):
             self.assertEqual(
-                [
-                    "bazel",
-                    "build",
-                    "//third_party/v8:release",
-                ],
-                rusty_v8_bazel.bazel_command(
-                    "build",
-                    "--config=ci-v8",
-                    "//third_party/v8:release",
-                ),
-            )
-        with patch.dict(environ, {"BUILDBUDDY_API_KEY": "token"}, clear=True):
-            self.assertEqual(
-                [
-                    "bazel",
-                    "build",
-                    "--config=buildbuddy-generic-rbe",
-                    "--remote_header=x-buildbuddy-api-key=token",
-                    "--config=ci-v8",
-                    "//third_party/v8:release",
-                ],
-                rusty_v8_bazel.bazel_command(
-                    "build",
-                    "--config=ci-v8",
-                    "//third_party/v8:release",
-                ),
+                ["--remote_header=x-buildbuddy-api-key=token"],
+                rusty_v8_bazel.bazel_remote_args(),
             )
 
-    def test_release_pair_labels_and_staged_names_distinguish_sandbox_artifacts(
-        self,
-    ) -> None:
+        with patch.dict(environ, {}, clear=True):
+            self.assertEqual([], rusty_v8_bazel.bazel_remote_args())
+
+    def test_release_pair_labels_and_staged_names_distinguish_sandbox_artifacts(self) -> None:
         self.assertEqual(
             "//third_party/v8:rusty_v8_release_pair_x86_64_unknown_linux_musl",
             rusty_v8_bazel.release_pair_label("x86_64-unknown-linux-musl"),
         )
         self.assertEqual(
             "//third_party/v8:rusty_v8_sandbox_release_pair_x86_64_unknown_linux_musl",
-            rusty_v8_bazel.release_pair_label(
-                "x86_64-unknown-linux-musl", sandbox=True
-            ),
+            rusty_v8_bazel.release_pair_label("x86_64-unknown-linux-musl", sandbox=True),
         )
         self.assertEqual(
             "//third_party/v8:rusty_v8_sandbox_release_pair_x86_64_apple_darwin",
@@ -230,7 +205,11 @@ class RustyV8BazelTest(unittest.TestCase):
         with TemporaryDirectory() as source_dir, TemporaryDirectory() as output_dir:
             source_root = Path(source_dir)
             gn_out = (
-                source_root / "target" / "x86_64-pc-windows-msvc" / "release" / "gn_out"
+                source_root
+                / "target"
+                / "x86_64-pc-windows-msvc"
+                / "release"
+                / "gn_out"
             )
             (gn_out / "obj").mkdir(parents=True)
             (gn_out / "obj" / "rusty_v8.lib").write_bytes(b"archive")