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/view_image.rs

@@ -362,12 +362,6 @@ console.log(out.output?.body?.text ?? "");
         .custom_tool_call_output_content_and_success(call_id)
         .expect("custom tool output present");
     let js_repl_output = js_repl_output.expect("custom tool output text present");
-    if js_repl_output.contains("Node runtime not found")
-        || js_repl_output.contains("Node runtime too old for js_repl")
-    {
-        eprintln!("Skipping js_repl image test: {js_repl_output}");
-        return Ok(());
-    }
     assert_ne!(
         js_repl_success,
         Some(false),