chore(lint): burn down remaining warnings to zero

src/channels/discord/adapter.test.ts

@@ -15,7 +15,10 @@ function createMockClient() {
     user: null as { id: string; tag: string } | null,
     on: vi.fn((event: string, handler: (...args: unknown[]) => void) => {
       if (!handlers.has(event)) {handlers.set(event, []);}
-      handlers.get(event)!.push(handler);
+      const eventHandlers = handlers.get(event);
+      if (eventHandlers) {
+        eventHandlers.push(handler);
+      }
     }),
     login: vi.fn(async (_token: string) => {
       // Set user info after login