Use turn environment settings for sandbox execution (#40771)

## Why

Tool execution can use an environment whose sandbox configuration differs from the turn-wide configuration. Sandbox selection and process setup need to follow the environment that owns the tool request.

## What changed

- Source Windows sandbox level, legacy Landlock mode, and Windows private desktop settings from the selected turn environment across tool orchestration, unified exec, patch application, and zsh fork escalation.
- Preserve Windows sandbox level overrides in restorable thread settings and invalidate MCP configuration when that level changes.

## Testing

- Add a resume test that verifies an elevated Windows sandbox override survives thread restoration.

GitOrigin-RevId: 9d8fc46404919f5ae97c9ed712c0932a1f095e36

codex-rs/core/src/unified_exec/process_manager.rs

@@ -1269,7 +1269,7 @@ impl UnifiedExecProcessManager {
                     approval_policy: turn.approval_policy(),
                     permission_profile: request.turn_environment.permission_profile().clone(),
                     environment_policy: request.turn_environment.config().exec_policy.as_ref(),
-                    windows_sandbox_level: turn.windows_sandbox_level,
+                    windows_sandbox_level: request.turn_environment.config().windows_sandbox_level,
                     sandbox_permissions: if request.additional_permissions_preapproved {
                         crate::sandboxing::SandboxPermissions::UseDefault
                     } else {