Dispose subprocess descendants after leader exit

docs/internal/adapters.md

@@ -57,14 +57,17 @@ configured filesystem secrets before adapter initialization.
 - 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
-  kill-on-close job object on Windows. Cancellation and deadlines request
-  termination, use a bounded forceful fallback, and wait for the leader before
-  returning. Child environments contain only the execution baseline and
-  adapter-specified values; configured credentials are explicit sensitive
-  values. Stdout and stderr are redacted while streaming into separate 8 MiB
-  diagnostic captures; a bounded wait closes a stream retained by a departed
-  leader's descendant. Reaching either limit terminates the owned tree.
-  Unsupported platforms reject owned command execution.
+  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;
+  Windows closes the job so kill-on-close applies. Cancellation, deadlines, and
+  diagnostic limits use the same terminal disposal path without losing their
+  original result classification. Child environments contain only the execution
+  baseline and adapter-specified values; configured credentials are explicit
+  sensitive values. Stdout and stderr are redacted while streaming into separate
+  8 MiB diagnostic captures; a bounded wait closes a stream retained by a
+  departed leader's descendant. Unsupported platforms reject owned command
+  execution.
 
 ## Implementation And Tests