Improve failover controls and preserve manual switching state

.tmp-tests/harbor-startup-recovery-KP1brk/bin/sing-box

@@ -0,0 +1,11 @@
+#!/usr/bin/env node
+const fs = require('node:fs');
+if (process.argv[2] === 'check') process.exit(0);
+if (process.argv[2] === 'version') {
+  console.log('sing-box version 1.13.18');
+  process.exit(0);
+}
+if (process.argv[2] === 'run') {
+  fs.appendFileSync(process.env.HARBOR_TEST_RUN_MARKER, 'run\n');
+  setInterval(() => {}, 60_000);
+}

.tmp-tests/harbor-startup-recovery-KP1brk/sing-box-config.json

@@ -0,0 +1 @@
+{"outbounds":[{"type":"vless","tag":"server-b","server":"b.example","server_port":8443},{"type":"direct","tag":"direct"}],"route":{"final":"server-b"}}

.tmp-tests/harbor-startup-recovery-KP1brk/state.json

@@ -0,0 +1 @@
+{"schemaVersion":6,"revision":4,"profiles":[{"id":"profile-a","label":"Основной","subscriptionUrl":"https://provider.example/subscription-a","subscriptionConfig":null,"servers":[{"id":"server-a","label":"Server A","host":"a.example","port":443,"protocol":"vless"}],"userInfo":{},"fetchedAt":null,"desiredServerId":"server-a","lastRefreshAttemptAt":null,"lastRefreshErrorCode":null}],"desiredProfileId":"profile-a","appliedProfileId":"profile-a","appliedServerId":"server-a","appliedServerSnapshot":{"id":"server-a","label":"Server A","host":"a.example","port":443,"protocol":"vless"},"routeRules":[],"appliedRouteRules":[],"routeRulesRevision":0,"connectionDesired":"running"}