fix(relay): keep orphan drain bounded by the scope-op timeout

The salvaged _close_scope_handle replaced direct scope.pop calls that
were bounded by _SCOPE_OP_TIMEOUT with an unbounded run_in_session
callback, regressing the bounded-finalization contract (CI:
tests/agent/test_relay_runtime_bounded_scope_ops.py — end_turn /
close_session / finish_logical_calls hung when the native pop wedged).
Pass timeout=_SCOPE_OP_TIMEOUT so the whole drain+close costs at most
one span and never blocks turn or session completion.

agent/relay_runtime.py

@@ -669,6 +669,11 @@ class RelayRuntime:
                 session,
                 close_with_drain,
                 allow_closing=allow_closing,
+                # Bound the whole drain+close like the direct pops it
+                # replaced: a wedged native pipeline must cost at most one
+                # span, never block turn/session completion (see
+                # tests/agent/test_relay_runtime_bounded_scope_ops.py).
+                timeout=_SCOPE_OP_TIMEOUT,
             )
         except Exception as exc:
             return f"{failure_label}: {exc}"