DUNGEONS-34: keep host screen awake while streaming

Co-authored-by: multica-agent <github@multica.ai>

frontend/composables/useKeepHostAwake.ts

@@ -0,0 +1,38 @@
+import { createScreenWakeLock, type WakeStatus } from "../utils/screenWakeLock";
+import type { Ref } from "vue";
+
+export function useKeepHostAwakePreference() {
+  return useCookie<boolean>("webka_keep_host_awake", {
+    default: () => false,
+    maxAge: 60 * 60 * 24 * 365,
+    sameSite: "lax",
+    path: "/",
+  });
+}
+
+export function useHostWakeLock(hosting: Ref<boolean>) {
+  const enabled = useKeepHostAwakePreference();
+  const status = ref<WakeStatus>("off");
+  let controller: ReturnType<typeof createScreenWakeLock> | undefined;
+  let unwatch: (() => void) | undefined;
+  const refresh = () => controller?.refresh();
+  onMounted(() => {
+    controller = createScreenWakeLock({
+      request: window.isSecureContext && navigator.wakeLock?.request
+        ? () => navigator.wakeLock.request("screen")
+        : undefined,
+      visible: () => document.visibilityState === "visible",
+      status: (value) => { status.value = value; },
+    });
+    unwatch = watch([enabled, hosting], () => {
+      controller?.update(enabled.value === true && hosting.value);
+    }, { immediate: true, flush: "sync" });
+    document.addEventListener("visibilitychange", refresh);
+  });
+  onBeforeUnmount(() => {
+    unwatch?.();
+    document.removeEventListener("visibilitychange", refresh);
+    controller?.dispose();
+  });
+  return { status, retry: refresh };
+}