Separate subprocess execution lifecycle from policy

docs/internal/adapters.md

@@ -71,7 +71,9 @@ configured filesystem secrets before adapter initialization.
 - Constructor errors fail stage execution setup early.
 - Runtime adapter errors propagate to stage code and then manifest failure handling.
 - Subprocess adapters persist stage logs/generated configs through stage-managed paths.
-- Shared subprocess execution starts an owned process group on Linux/macOS or a
+- Shared subprocess execution keeps private lifecycle mechanics separate from
+  Narratio's environment, diagnostics, redaction, and error policy. It starts
+  an owned process group on Linux/macOS or a
   kill-on-close job object on Windows. Every terminal path disposes of that
   owned tree before returning. After a natural leader exit, Unix checks for
   remaining group members and uses bounded graceful then forceful termination;