feat(companion): add runtime event subscription hooks

src/companion/runtimeClient.ts

@@ -41,6 +41,8 @@ export interface CompanionRuntimeClientOptions {
   websocketFactory?: (url: string) => WebSocket;
 }
 
+export type CompanionEventHandler = (event: string, data: unknown) => void;
+
 export interface RegisterNodeInput {
   nodeId: string;
   role: string;
@@ -257,6 +259,7 @@ export class CompanionRuntimeClient {
   private connectPromise: Promise<void> | null = null;
   private nextId = 1;
   private pending = new Map<number, PendingRequest>();
+  private readonly eventHandlers = new Set<CompanionEventHandler>();
 
   constructor(options: CompanionRuntimeClientOptions) {
     this.url = options.url;
@@ -342,6 +345,13 @@ export class CompanionRuntimeClient {
     ws.close(code, reason);
   }
 
+  subscribeEvents(handler: CompanionEventHandler): () => void {
+    this.eventHandlers.add(handler);
+    return () => {
+      this.eventHandlers.delete(handler);
+    };
+  }
+
   async call<T>(method: string, params?: Record<string, unknown>): Promise<T> {
     if (!this.connected) {
       if (!this.autoConnect) {
@@ -498,6 +508,13 @@ export class CompanionRuntimeClient {
     }
 
     if ('event' in parsed) {
+      for (const handler of this.eventHandlers) {
+        try {
+          handler(parsed.event, parsed.data);
+        } catch {
+          // Event subscribers are userland callbacks; isolate failures.
+        }
+      }
       return;
     }