fix: add close() lifecycle methods to all adapters, fix WS client handler preservation, add Worker thread context guard

- Add close() to Redis, WS Client, WS Server, Worker Host, Worker Thread adapters
  for graceful teardown (cleanup subscriptions, restore handlers, clear maps)
- WS Client now saves/restores original onmessage (consistent with WS Server)
- WS Client dispatchEvent/addEventListener/removeEventListener are no-ops after close()
- WS Server close() removes all connections and clears local listeners
- Redis close() unsubscribes all channels and removes message listener
- Worker Host/Thread close() restore original onmessage and clear callbacks
- Worker Thread throws clear error if globalThis.postMessage is unavailable
- Add double-call guard to WS Server removeConnection
- Export new adapter interface types (RedisEventTarget, WebSocketClientEventTarget, etc.)
- Add sideEffects: false to package.json for tree-shaking
- Update architecture docs: lifecycle section, close() contract, adapter status updates
- 22 new tests covering close(), handler restoration, idempotency, and context guard

test/event-target-websocket-client.test.ts

@@ -626,6 +626,100 @@ describe("createWebSocketClientEventTarget", () => {
     });
   });
 
+  describe("close()", () => {
+    it("sends __unsubscribe for all active subscriptions", () => {
+      const ws = createMockWebSocket();
+      const eventTarget = createWebSocketClientEventTarget<TestEvent>(ws as any);
+
+      const listener1 = vi.fn();
+      const listener2 = vi.fn();
+      eventTarget.addEventListener("topic:a", listener1);
+      eventTarget.addEventListener("topic:b", listener2);
+
+      (ws.send as ReturnType<typeof vi.fn>).mockClear();
+
+      eventTarget.close();
+
+      const sent = ws.sent.map((s: string) => JSON.parse(s));
+      const unsubscribes = sent.filter((e: any) => e.type === "__unsubscribe");
+      expect(unsubscribes).toHaveLength(2);
+      const topics = unsubscribes.map((e: any) => e.payload.topic);
+      expect(topics).toContain("topic:a");
+      expect(topics).toContain("topic:b");
+    });
+
+    it("restores original onmessage handler", () => {
+      const ws = createMockWebSocket();
+      const originalOnmessage = vi.fn();
+      ws.onmessage = originalOnmessage;
+
+      const eventTarget = createWebSocketClientEventTarget<TestEvent>(ws as any);
+      expect(ws.onmessage).not.toBe(originalOnmessage);
+
+      eventTarget.close();
+
+      expect(ws.onmessage).toBe(originalOnmessage);
+    });
+
+    it("does not deliver messages after close", () => {
+      const ws = createMockWebSocket();
+      const eventTarget = createWebSocketClientEventTarget<TestEvent>(ws as any);
+
+      const listener = vi.fn();
+      eventTarget.addEventListener("topic:a", listener);
+
+      eventTarget.close();
+
+      const envelope: EventEnvelope = { type: "topic", id: "a", payload: "hello" };
+      ws.simulateMessage(JSON.stringify(envelope));
+
+      expect(listener).not.toHaveBeenCalled();
+    });
+
+    it("does not send __subscribe after close", () => {
+      const ws = createMockWebSocket();
+      const eventTarget = createWebSocketClientEventTarget<TestEvent>(ws as any);
+      eventTarget.close();
+
+      const listener = vi.fn();
+      eventTarget.addEventListener("topic:a", listener);
+
+      expect(ws.send).not.toHaveBeenCalledWith(
+        expect.stringContaining("__subscribe"),
+      );
+    });
+
+    it("dispatchEvent returns true but does not send after close", () => {
+      const ws = createMockWebSocket();
+      const eventTarget = createWebSocketClientEventTarget<TestEvent>(ws as any);
+      eventTarget.close();
+
+      (ws.send as ReturnType<typeof vi.fn>).mockClear();
+
+      const event = new CustomEvent("test:event", {
+        detail: { type: "test", id: "event", payload: null },
+      }) as TestEvent;
+
+      const result = eventTarget.dispatchEvent(event);
+      expect(result).toBe(true);
+      expect(ws.send).not.toHaveBeenCalled();
+    });
+
+    it("is idempotent", () => {
+      const ws = createMockWebSocket();
+      const eventTarget = createWebSocketClientEventTarget<TestEvent>(ws as any);
+
+      const listener = vi.fn();
+      eventTarget.addEventListener("topic:a", listener);
+
+      eventTarget.close();
+      eventTarget.close();
+
+      const sentCalls = ws.sent.filter((s: string) => JSON.parse(s).type === "__unsubscribe");
+      expect(sentCalls).toHaveLength(1);
+    });
+  });
+
   describe("dispatchEvent (send path) edge cases", () => {
     it("sends envelope with null payload", () => {
       const ws = createMockWebSocket();