chore(node): cover the sync tick's online prune from the job package

The traffic sync's call that drops online sets of nodes it no longer
fetches had no test: a job-package test cannot install an xray process,
so online state was invisible there and removing the call passed.

SetXrayProcessForTest installs a test process for tests in other packages,
the same kind of seam as Manager.SetRuntimeOverride. The new job test runs
a real tick with a disabled node and a deleted one and fails without the
call.

internal/web/service/xray_process_test_seam.go

@@ -0,0 +1,16 @@
+package service
+
+import "github.com/mhsanaei/3x-ui/v3/internal/xray"
+
+// SetXrayProcessForTest installs p as the running process and returns the restore func,
+// so tests in other packages can observe online state. Never call it in production.
+func SetXrayProcessForTest(p *xray.Process) (restore func()) {
+	previousProcess, previousResult := xrayState.snapshot()
+	xrayState.replace(p)
+	return func() {
+		xrayState.mu.Lock()
+		xrayState.process = previousProcess
+		xrayState.result = previousResult
+		xrayState.mu.Unlock()
+	}
+}