One guarded handler slot for a bundle's event and heartbeat handlers, so a reload never races the consumer's loop

Claude-Session: https://claude.ai/code/session_01JG73KJNrH5EgFXMKKYSrig

node-tools/internal/runtime/reload_test.go

@@ -343,7 +343,7 @@ func TestAnEventHeardDuringAReloadIsOfferedAgainNotAPanic(t *testing.T) {
 	c := &consumers{logf: func(string, ...any) {}, of: map[string]*moduleEvents{}}
 	var got []string
 	before := func(json.RawMessage) error { got = append(got, "before"); return nil }
-	old := &moduleEvents{delivers: []*func(json.RawMessage) error{&before}}
+	old := &moduleEvents{delivers: []*deliverSlot{{f: before}}}
 	c.of["ledger"] = old
 	c.dropModule("ledger")
 	env := bus.Envelope{Key: "alpha.happened", Body: json.RawMessage(`{"n":1}`)}
@@ -359,7 +359,7 @@ func TestAnEventHeardDuringAReloadIsOfferedAgainNotAPanic(t *testing.T) {
 		t.Error("an event heard while the module is loaded again was taken, not offered again")
 	}
 	after := func(json.RawMessage) error { got = append(got, "after"); return nil }
-	fresh := &moduleEvents{delivers: []*func(json.RawMessage) error{&after}}
+	fresh := &moduleEvents{delivers: []*deliverSlot{{f: after}}}
 	c.of["ledger"] = fresh
 	if err := hand(fresh); err != nil {
 		t.Errorf("the bundle loaded again was not handed the event: %v", err)