tests(js_repl): remove node-related skip paths from js_repl tests (#12185)

## Summary
Remove js_repl/node test-skip paths and make Node setup explicit in CI
so js_repl tests always run instead of silently skipping.

## Why
We had multiple “expediency” skip paths that let js_repl tests pass
without actually exercising Node-backed behavior. This reduced CI signal
and hid runtime/environment regressions.

## What changed

### CI
- Added Node setup using `codex-rs/node-version.txt` in:
  - `.github/workflows/rust-ci.yml`
  - `.github/workflows/bazel.yml`
- Added a Unix PATH copy step in Bazel workflow to expose the setup-node
binary in common paths.

### js_repl test harness
- Added explicit js_repl sandbox test configuration helpers in:
  - `codex-rs/core/src/tools/js_repl/mod.rs`
  - `codex-rs/core/src/tools/handlers/js_repl.rs`
- Added Linux arg0 dispatch glue for js_repl tests so sandbox subprocess
entrypoint behavior is correct under Linux test execution.

### Removed skip behavior
- Deleted runtime guard function and early-return skips in js_repl tests
(`can_run_js_repl_runtime_tests` and related per-test short-circuits).
- Removed view_image integration test skip behavior:
  - dropped `skip_if_no_network!(Ok(()))`
- removed “skip on Node missing/too old” branch after js_repl output
inspection.

## Impact
- js_repl/node tests now consistently execute and fail loudly when the
environment is not correctly provisioned.
- CI has stronger signal for js_repl regressions instead of false green
from conditional skips.

## Testing
- `cargo test -p codex-core` (locally) to validate js_repl
unit/integration behavior with skips removed.
- CI expected to surface any remaining environment/runtime gaps directly
(rather than masking them).


#### [git stack](https://github.com/magus/git-stack-cli)
- ✅ `1` https://github.com/openai/codex/pull/12300
- ✅ `2` https://github.com/openai/codex/pull/12275
- ✅ `3` https://github.com/openai/codex/pull/12205
- ✅ `4` https://github.com/openai/codex/pull/12407
- ✅ `5` https://github.com/openai/codex/pull/12372
- 👉 `6` https://github.com/openai/codex/pull/12185
- ⏳ `7` https://github.com/openai/codex/pull/10673

codex-rs/core/tests/suite/js_repl.rs

@@ -12,7 +12,6 @@ use core_test_support::responses::ev_response_created;
 use core_test_support::responses::sse;
 use core_test_support::skip_if_no_network;
 use core_test_support::test_codex::test_codex;
-use which::which;
 use wiremock::MockServer;
 
 fn custom_tool_output_text_and_success(
@@ -55,25 +54,10 @@ async fn run_js_repl_turn(
     Ok(second_mock)
 }
 
-fn can_run_js_repl_runtime_tests() -> bool {
-    // In the base CI-stabilization commit, skip these integration tests only
-    // when the js_repl Node runtime is not available. A later stacked commit
-    // removes this automatic skip and requires them everywhere.
-    if let Some(path) = std::env::var_os("CODEX_JS_REPL_NODE_PATH")
-        && std::path::Path::new(&path).exists()
-    {
-        return true;
-    }
-    which("node").is_ok()
-}
 #[tokio::test(flavor = "multi_thread", worker_threads = 2)]
 async fn js_repl_persists_top_level_bindings_and_supports_tla() -> Result<()> {
     skip_if_no_network!(Ok(()));
 
-    if !can_run_js_repl_runtime_tests() {
-        return Ok(());
-    }
-
     let server = responses::start_mock_server().await;
     let mut builder = test_codex().with_config(|config| {
         config.features.enable(Feature::JsRepl);
@@ -138,10 +122,6 @@ async fn js_repl_persists_top_level_bindings_and_supports_tla() -> Result<()> {
 async fn js_repl_can_invoke_builtin_tools() -> Result<()> {
     skip_if_no_network!(Ok(()));
 
-    if !can_run_js_repl_runtime_tests() {
-        return Ok(());
-    }
-
     let server = responses::start_mock_server().await;
     let mock = run_js_repl_turn(
         &server,
@@ -169,10 +149,6 @@ async fn js_repl_can_invoke_builtin_tools() -> Result<()> {
 async fn js_repl_tool_call_rejects_recursive_js_repl_invocation() -> Result<()> {
     skip_if_no_network!(Ok(()));
 
-    if !can_run_js_repl_runtime_tests() {
-        return Ok(());
-    }
-
     let server = responses::start_mock_server().await;
     let mock = run_js_repl_turn(
         &server,
@@ -214,10 +190,6 @@ try {
 async fn js_repl_does_not_expose_process_global() -> Result<()> {
     skip_if_no_network!(Ok(()));
 
-    if !can_run_js_repl_runtime_tests() {
-        return Ok(());
-    }
-
     let server = responses::start_mock_server().await;
     let mock = run_js_repl_turn(
         &server,
@@ -242,10 +214,6 @@ async fn js_repl_does_not_expose_process_global() -> Result<()> {
 async fn js_repl_blocks_sensitive_builtin_imports() -> Result<()> {
     skip_if_no_network!(Ok(()));
 
-    if !can_run_js_repl_runtime_tests() {
-        return Ok(());
-    }
-
     let server = responses::start_mock_server().await;
     let mock = run_js_repl_turn(
         &server,