Run core integration tests against a Wine-backed Windows executor (#28401)

## Why

We want to exercise a linux app-server against a windows exec-server
without having to repeat every test case. This approach has slight
precedent in the remote docker test setup.

## What

Run the shared `codex-core` integration suite against Windows
exec-server behavior from Linux. This makes cross-OS path and shell
regressions visible while keeping unsupported cases owned by individual
tests.

- Add `local`, `docker`, and `wine-exec` test environment selection with
legacy Docker compatibility.
- Extend `codex_rust_crate` to generate a sharded Wine-exec variant
using a cross-built Windows server and pinned Bazel Wine/PowerShell
runtimes.
- Teach remote-aware helpers about Windows paths and track temporary
incompatibilities with source-local `skip_if_wine_exec!` calls and
follow-up reasons.

.codex/skills/remote-tests/SKILL.md

@@ -3,12 +3,15 @@ name: remote-tests
 description: How to run tests using remote executor.
 ---
 
-Some codex integration tests support a running against a remote executor.
-This means that when CODEX_TEST_REMOTE_ENV environment variable is set they will attempt to start an executor process in a docker container CODEX_TEST_REMOTE_ENV points to and use it in tests.
+Some Codex integration tests select `local`, `docker`, or `wine-exec` through
+`CODEX_TEST_ENVIRONMENT`. The legacy `CODEX_TEST_REMOTE_ENV=<container>` still
+selects Docker; otherwise execution is local.
 
 Docker container is built and initialized via ./scripts/test-remote-env.sh
 
-Currently running remote tests is only supported on Linux, so you need to use a devbox to run them
+On x86-64 Linux, run Wine exec with
+`bazel test //codex-rs/core:core-all-wine-exec-test --test_output=errors`.
+Temporary blockers belong beside the test in `skip_if_wine_exec!` calls.
 
 You can list devboxes via `applied_devbox ls`, pick the one with `codex` in the name.
 Connect to devbox via `ssh <devbox_name>`.