Add core.status RPC, RPC invite diagnostics, and WebSocket stats refresh

- core.status handler and coreStatusRequest; diagnoseInviteIssuesAsync
  clears stale failed-invite flags when peers report canProvideInvite
- Admin invite diagnostics and Core stats UI: per-peer remote state,
  text status marks, recommendations aligned with invite.deliver RPC
- Extract stats-collector; push stats/health/status via subscribe-stats
  WebSocket; HTTP only on first Stats tab load
- Document core.status in PLUGIN_SDK; proxy registers onCoreStatus

test-scripts/core-swarm-handlers.test.js

@@ -92,11 +92,56 @@ function testNoLegacyAdapterInP2ns() {
 
 function testMethodsIncludeDeliver() {
   assert.strictEqual(METHODS.INVITE_DELIVER, 'invite.deliver');
+  assert.strictEqual(METHODS.CORE_STATUS, 'core.status');
   assert.ok(INVITE_STATUS.OK);
 }
 
+function testCoreStatusMaster() {
+  const handlers = createCoreSwarmHandlers({
+    Autopass: {},
+    store: {},
+    core: { writable: true, update: async () => {} },
+    state: { consecutiveInviteFailures: 0, pendingInviteRequests: new Map() },
+    isMaster: true,
+    getDnsPass: () => ({}),
+    setDnsPass: () => {},
+    connectedPeers: new Set(['peer1', 'peer2']),
+    peerChannels: new Map(),
+    failedInvitePeers: new Set(),
+    pendingInviteAcks: new Map(),
+    pendingInviteRequestHandlers: new Set(),
+    isProcessingInvite: () => false,
+    acquireInviteLock: async () => {},
+    releaseInviteLock: () => {},
+    withTimeout: (p) => p,
+    getCurrentInvitePromise: () => null,
+    setCurrentInvitePromise: () => {},
+    getCurrentPairOperation: () => null,
+    setCurrentPairOperation: () => {},
+    setupDomainsWatcher: () => {},
+    listDomains: async () => [],
+    doAutoVotes: () => {},
+    setupListeners: () => {},
+    coreRpc: {},
+    channelManager: { getChannelInfo: () => null, waitForBidirectionalOpen: async () => true },
+    CORE_DOMAIN: 'p2ns.core'
+  });
+
+  return handlers.onCoreStatus().then((status) => {
+    assert.strictEqual(status.nodeType, 'master');
+    assert.strictEqual(status.dnsPassInitialized, true);
+    assert.strictEqual(status.canProvideInvite, true);
+    assert.strictEqual(status.connectedPeers, 2);
+  });
+}
+
 testInviteAckClearsPending();
 testInviteAckIgnoresStaleId();
 testNoLegacyAdapterInP2ns();
 testMethodsIncludeDeliver();
-console.log('core-swarm-handlers.test: ok');
+testCoreStatusMaster().then(() => {
+  console.log('core-swarm-handlers.test: ok');
+}).catch((err) => {
+  console.error(err);
+  process.exit(1);
+});