## Why
Bazel-backed end-to-end macrobenchmark plumbing needs a small,
deterministic first consumer that does not couple the shared
infrastructure to the remote-skill scenario.
## What
- add `codex_e2e_benchmark`, a small macro for Bazel-only Divan
benchmarks and runtime binary runfiles
- keep benchmark sources under `e2e_benches/` so Cargo does not
auto-discover them
- add a CLI example that resolves the real `codex` binary and measures
`codex --help`
- assert the spawned command succeeds
## Validation
- `bazel test --compilation_mode=fastbuild
--@rules_rust//rust/settings:extra_rustc_flag=-Cdebug-assertions=no
--@rules_rust//rust/settings:extra_exec_rustc_flag=-Cdebug-assertions=no
--cache_test_results=no --test_output=errors --test_arg=--test
//codex-rs/cli:codex-help-bench`
## Stack
1. [#31295 bench: add codex help e2e
macrobenchmark](https://github.com/openai/codex/pull/31295)
2. [#31428 bench: add e2e benchmark
entrypoints](https://github.com/openai/codex/pull/31428)
3. [#31429 ci: smoke Bazel e2e
benchmarks](https://github.com/openai/codex/pull/31429)
