feat(streaming): introduce WebSocket Streaming API bridging event bus

ApiServer: add AsyncWebSocket at /ws; accept JSON {event, payload} (string or object) and dispatch via ctx.fire; mirror all local events to clients using NodeContext::onAny.\nNodeContext: add onAny subscriber API.\nNeoPatternService: add api/neopattern/color event to set solid color.\nCluster: centralize cluster/broadcast sending in core; services delegate.\nAPI: add generic /api/node/event and /api/cluster/event endpoints in respective services.\nTests: add ws-color-client, ws-cluster-broadcast-color, http-cluster-broadcast-color.\nDocs: add StreamingAPI.md; update README and test/README.\nFixes: robust WS JSON parsing on ESP8266 and payload handling.

test/node_modules/ws/lib/limiter.js

@@ -0,0 +1,55 @@
+'use strict';
+
+const kDone = Symbol('kDone');
+const kRun = Symbol('kRun');
+
+/**
+ * A very simple job queue with adjustable concurrency. Adapted from
+ * https://github.com/STRML/async-limiter
+ */
+class Limiter {
+  /**
+   * Creates a new `Limiter`.
+   *
+   * @param {Number} [concurrency=Infinity] The maximum number of jobs allowed
+   *     to run concurrently
+   */
+  constructor(concurrency) {
+    this[kDone] = () => {
+      this.pending--;
+      this[kRun]();
+    };
+    this.concurrency = concurrency || Infinity;
+    this.jobs = [];
+    this.pending = 0;
+  }
+
+  /**
+   * Adds a job to the queue.
+   *
+   * @param {Function} job The job to run
+   * @public
+   */
+  add(job) {
+    this.jobs.push(job);
+    this[kRun]();
+  }
+
+  /**
+   * Removes a job from the queue and runs it if possible.
+   *
+   * @private
+   */
+  [kRun]() {
+    if (this.pending === this.concurrency) return;
+
+    if (this.jobs.length) {
+      const job = this.jobs.shift();
+
+      this.pending++;
+      job(this[kDone]);
+    }
+  }
+}
+
+module.exports = Limiter;