fix: apply_patch shell_serialization tests (#4786)

## Summary
Adds additional shell_serialization tests specifically for apply_patch
and other cases.

## Test Plan
- [x] These are all tests

codex-rs/core/tests/common/test_codex.rs

@@ -1,4 +1,5 @@
 use std::mem::swap;
+use std::path::PathBuf;
 use std::sync::Arc;
 
 use codex_core::CodexAuth;
@@ -39,6 +40,12 @@ impl TestCodexBuilder {
         let mut config = load_default_config_for_test(&home);
         config.cwd = cwd.path().to_path_buf();
         config.model_provider = model_provider;
+        config.codex_linux_sandbox_exe = Some(PathBuf::from(
+            assert_cmd::Command::cargo_bin("codex")?
+                .get_program()
+                .to_os_string(),
+        ));
+
         let mut mutators = vec![];
         swap(&mut self.config_mutators, &mut mutators);