fix(e2e): inherit PATHEXT on Windows for executable lookup

When using native bash with env_clear(), the child process loses
PATHEXT which is needed by the which crate to find executables
with extensions like .exe and .cmd on Windows.

Co-Authored-By: Claude Opus 4.5 <noreply@anthropic.com>

Author: branchseer

crates/vite_task_bin/tests/e2e_snapshots/main.rs

@@ -163,7 +163,6 @@ fn run_case_inner(tmpdir: &AbsolutePath, fixture_path: &Path, fixture_name: &str
             let mut cmd = Command::new(&shell_exe);
             cmd.arg("-c")
                 .arg(step.cmd())
-                .env_clear()
                 .env("PATH", &e2e_env_path)
                 .env("NO_COLOR", "1")
                 .current_dir(e2e_stage_path.join(&e2e.cwd));