fix(distributed): restore node liveness tests (#11694)

* fix(distributed): restore node liveness tests

The router now probes models.running before it schedules work. The E2E
workers only mocked backend.install, so every test node appeared offline.

The endpoint test double also missed the new PingNode method and stopped
the Linux, Apple, and lint jobs during compilation.

Mock the existing worker reply in both distributed fixtures and keep the
endpoint test double aligned with NodeCommandSender.

Assisted-by: Codex:gpt-5 [golangci-lint]

* fix(tests): check node liveness replies

The liveness test subscriptions ignored setup and reply errors.

Errcheck rejected each branch that carried them.

Assisted-by: Codex:gpt-5 [golangci-lint]

---------

Co-authored-by: localai-org-maint-bot <306269227+localai-org-maint-bot@users.noreply.github.com>

tests/e2e/distributed/distributed_full_flow_test.go

@@ -260,6 +260,12 @@ var _ = Describe("Full Distributed Inference Flow", Label("Distributed"), func()
 			data, _ := json.Marshal(reply)
 			msg.Respond(data)
 		})
+		_, err := infra.NC.Conn().Subscribe("nodes.*.models.running", func(msg *nats.Msg) {
+			data, _ := json.Marshal(messaging.ModelsRunningReply{})
+			_ = msg.Respond(data)
+		})
+		Expect(err).NotTo(HaveOccurred())
+		FlushNATS(infra.NC)
 
 		return router
 	}

tests/e2e/distributed/router_tracking_test.go

@@ -66,6 +66,12 @@ var _ = Describe("SmartRouter trackingKey", Label("Distributed"), func() {
 			data, _ := json.Marshal(reply)
 			msg.Respond(data)
 		})
+		_, err = infra.NC.Conn().Subscribe("nodes.*.models.running", func(msg *nats.Msg) {
+			data, _ := json.Marshal(messaging.ModelsRunningReply{})
+			_ = msg.Respond(data)
+		})
+		Expect(err).NotTo(HaveOccurred())
+		FlushNATS(infra.NC)
 
 		// Start a mock gRPC backend using the same helper as full flow tests
 		llm := &trackingTestLLM{}