F-tools: the runner's views consumer is proven on the real bus; the heartbeat is asked of the bus only when a bundle wants it, with no race; a seat record says when the bus wrote it; the beat test counts ticks, not sleeps

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

node-tools/internal/bus/export_test.go

@@ -0,0 +1,8 @@
+package bus
+
+// SetTickHook makes the next consumes call f after each idle heartbeat interval was handled; the restore puts it back.
+func SetTickHook(f func()) (restore func()) {
+	old := tickHook
+	tickHook = f
+	return func() { tickHook = old }
+}