feat(server): stream replayable harness events

apps/server/src/sse/sse-registry.ts

@@ -0,0 +1,35 @@
+import type { SseConnection } from "./sse-connection.js";
+
+export interface SseRegistryPort {
+  add(sessionId: string, connection: SseConnection): void;
+  remove?(sessionId: string, connection: SseConnection): void;
+  closeForSession(sessionId: string): void;
+  closeAll(): void;
+}
+
+export class SseRegistry implements SseRegistryPort {
+  readonly #connections = new Map<string, Set<SseConnection>>();
+
+  public add(sessionId: string, connection: SseConnection): void {
+    const existing = this.#connections.get(sessionId);
+    if (existing !== undefined) existing.add(connection);
+    else this.#connections.set(sessionId, new Set([connection]));
+  }
+
+  public remove(sessionId: string, connection: SseConnection): void {
+    const existing = this.#connections.get(sessionId);
+    existing?.delete(connection);
+    if (existing?.size === 0) this.#connections.delete(sessionId);
+  }
+
+  public closeForSession(sessionId: string): void {
+    const connections = this.#connections.get(sessionId);
+    if (connections === undefined) return;
+    this.#connections.delete(sessionId);
+    for (const connection of [...connections]) connection.close();
+  }
+
+  public closeAll(): void {
+    for (const sessionId of [...this.#connections.keys()]) this.closeForSession(sessionId);
+  }
+}