feat(cli): add sandbox profile config controls (#20118)

## Why

The explicit profile path from #20117 is meant for standalone testing,
but it still inherited the
shell cwd and all managed requirements implicitly. The pre-existing
launcher path even called out
that it did not support a separate cwd yet in

[`debug_sandbox.rs`](https://github.com/openai/codex/blob/509453f688a30929432be866402d1ea46aa12169/codex-rs/cli/src/debug_sandbox.rs#L174-L179).

For a standalone command, the useful default is to let the caller choose
the project directory being
tested and to avoid administrator-provided constraints unless the caller
explicitly wants to test
those too.

## What changed

- Add explicit-profile-only `-C/--cd DIR`, and use that cwd for both
profile resolution and command
  execution.
- Add explicit-profile-only `--include-managed-config`.
- Make explicit profile mode skip managed requirement sources by
default, including cloud
requirements, MDM requirements, `/etc/codex/requirements.toml`, and the
legacy managed-config
  requirements projection.
- Preserve all existing invocations outside the explicit-profile path.

## Stack

1. #20117 `sandbox-ui-profile`
2. #20118 `sandbox-ui-config` --> this PR

Both PRs are additive. Replay JSON is intentionally deferred to a
follow-up design pass.

## Tests ran

- `cargo test -p codex-cli debug_sandbox`
- `cargo test -p codex-cli sandbox_macos_`
- `cargo test -p codex-core
load_config_layers_can_ignore_managed_requirements`
- `cargo test -p codex-core
load_config_layers_includes_cloud_requirements`
- macOS branch-binary smoke on the rebased top of stack: `-C` changed
execution cwd, explicit
profile mode omitted managed proxy env under `env -i`, and
`--include-managed-config` restored it.
- Linux devbox branch-binary smoke on the rebased top of stack: `-C`
changed execution cwd for
  built-in and user-defined explicit profiles.

codex-rs/core/src/config/config_loader_tests.rs

@@ -1084,6 +1084,58 @@ async fn load_config_layers_includes_cloud_requirements() -> anyhow::Result<()>
     Ok(())
 }
 
+#[tokio::test]
+async fn load_config_layers_can_ignore_managed_requirements() -> anyhow::Result<()> {
+    let tmp = tempdir()?;
+    let codex_home = tmp.path().join("home");
+    tokio::fs::create_dir_all(&codex_home).await?;
+    let cwd = AbsolutePathBuf::from_absolute_path(tmp.path())?;
+
+    let managed_config_path = tmp.path().join("managed_config.toml");
+    tokio::fs::write(&managed_config_path, "approval_policy = \"never\"\n").await?;
+    let system_requirements_path = tmp.path().join("requirements.toml");
+    tokio::fs::write(
+        &system_requirements_path,
+        "allowed_sandbox_modes = [\"read-only\"]\n",
+    )
+    .await?;
+
+    let mut overrides = LoaderOverrides::with_managed_config_path_for_tests(managed_config_path);
+    overrides.system_requirements_path = Some(system_requirements_path);
+    overrides.ignore_managed_requirements = true;
+
+    let cloud_requirements = CloudRequirementsLoader::new(async {
+        Ok(Some(ConfigRequirementsToml {
+            allowed_approval_policies: Some(vec![AskForApproval::Never]),
+            ..Default::default()
+        }))
+    });
+
+    let mut config = ConfigBuilder::default()
+        .codex_home(codex_home)
+        .fallback_cwd(Some(cwd.to_path_buf()))
+        .loader_overrides(overrides)
+        .cloud_requirements(cloud_requirements)
+        .build()
+        .await?;
+
+    assert!(
+        config
+            .permissions
+            .approval_policy
+            .can_set(&AskForApproval::OnRequest)
+            .is_ok(),
+        "ignoring managed requirements should leave on-request approval allowed"
+    );
+    config
+        .permissions
+        .approval_policy
+        .set(AskForApproval::OnRequest)
+        .expect("ignoring managed requirements should allow setting on-request approval");
+
+    Ok(())
+}
+
 #[tokio::test]
 async fn load_config_layers_includes_cloud_hook_requirements() -> anyhow::Result<()> {
     let tmp = tempdir()?;