pagescene: finish anonymous-use polish

- Gate File → Load my scene for anon: route through promptSignup
  instead of opening a dialog that would just error-toast on the
  silent listUserMediaFiles failure.
- Remove dead SettingsModal mount in Controls3D (no UI ever triggered
  it). Drops the @storyteller/ui-settings-modal import from this file.
- New AnonHintChip pill in the top-right corner of the playground
  ("Sign up to save"). Renders only when currentUserToken is undefined
  AND not in view-only mode; click routes to promptSignup. Tauri users
  never see it.
- Scaffolding for view-only PreviewBox: new component renders a small
  card with the author's generation result; returns null when no URL
  is supplied. Mounted in Stage3DBody under the isViewOnly guard,
  reading sceneMeta.previewImageUrl (new optional field). Data-path
  wiring (populating previewImageUrl from adapter.loadScene's
  response) is the next step — leaving the UI plumbing in place so
  that follow-up is purely data, not layout surgery.

frontend/libs/components/pagescene/src/index.ts

@@ -187,6 +187,7 @@ export { getSceneGenerationMetaData } from "./lib/sceneMetadata";
 // signalScene, addToast, loadingBarData/IsShowing signals, etc.)
 // are either surfaced via adapter slots or replaced with
 // lib-internal state.
+export { AnonHintChip } from "./lib/comps/AnonHintChip";
 export { AssetMenu, AssetModal } from "./lib/comps/AssetMenu";
 export { Controls3D } from "./lib/comps/Controls3D";
 export { ControlsTopButtons } from "./lib/comps/ControlsTopButtons";
@@ -199,6 +200,8 @@ export { EditorCanvas, CameraViewCanvas } from "./lib/comps/EngineCanvases";
 export { Outliner } from "./lib/comps/Outliner";
 export { ControlPanelSceneObject } from "./lib/comps/ControlPanelSceneObject";
 export { SceneContainer } from "./lib/comps/SceneContainer";
+export { PreviewBox } from "./lib/comps/PreviewBox";
+export type { PreviewBoxProps } from "./lib/comps/PreviewBox";
 export { PreviewEngineCamera } from "./lib/comps/PreviewEngineCamera";
 export { PreviewImages } from "./lib/comps/PreviewImages";
 export { OnboardingHelper } from "./lib/comps/OnboardingHelper";

frontend/libs/components/pagescene/src/lib/PageSceneStore.ts

@@ -22,6 +22,10 @@ export interface SceneMeta {
   ownerToken: string | undefined;
   isModified: boolean | undefined;
   isInitializing: boolean;
+  // URL to the author's generation result for this scene, shown in
+  // view-only mode's PreviewBox. Host populates this from the
+  // adapter.loadScene response. Optional; absent ⇒ no preview rendered.
+  previewImageUrl?: string;
 }
 
 export type SceneObjectKind = "object" | "character" | "shape";

frontend/libs/components/pagescene/src/lib/Stage3DBody.tsx

@@ -33,6 +33,7 @@ import type { PopoverItem } from "@storyteller/ui-popover";
 import { v4 as uuidv4 } from "uuid";
 
 import { EngineContext } from "./contexts/EngineContext/EngineContext";
+import { AnonHintChip } from "./comps/AnonHintChip";
 import { ControlPanelSceneObject } from "./comps/ControlPanelSceneObject";
 import { Controls3D } from "./comps/Controls3D";
 import { ControlsTopButtons } from "./comps/ControlsTopButtons";
@@ -41,6 +42,7 @@ import { FocalLengthDisplay } from "./comps/FocalLengthDisplay/FocalLengthDispla
 import { OnboardingHelper } from "./comps/OnboardingHelper";
 import { Outliner } from "./comps/Outliner";
 import { PoseModeSelector } from "./comps/PoseModeSelector";
+import { PreviewBox } from "./comps/PreviewBox";
 import { PreviewEngineCamera } from "./comps/PreviewEngineCamera";
 import { SceneContainer } from "./comps/SceneContainer";
 import { addCharacter, addObject, setCameraAspect } from "./actions";
@@ -74,6 +76,7 @@ export const Stage3DBody = () => {
     (s) => s.setIsPromptBoxFocused,
   );
   const gridVisible = usePageSceneStore((s) => s.gridVisible);
+  const previewImageUrl = usePageSceneStore((s) => s.sceneMeta.previewImageUrl);
   const isViewOnly = useIsViewOnly();
   const addCamera = usePageSceneStore((s) => s.addCamera);
   const updateCamera = usePageSceneStore((s) => s.updateCamera);
@@ -344,6 +347,9 @@ export const Stage3DBody = () => {
                 <div className="grid grid-cols-3 gap-4">
                   <ControlsTopButtons />
                   <Controls3D />
+                  <div className="flex items-start justify-end gap-2 pr-2 pt-2">
+                    <AnonHintChip />
+                  </div>
                 </div>
               </div>
             )}
@@ -364,8 +370,7 @@ export const Stage3DBody = () => {
               {!isViewOnly && <ControlPanelSceneObject />}
             </div>
 
-            {/* Future: <PreviewBox /> slot when isViewOnly — shows the
-                author's generated still next to the camera. */}
+            {isViewOnly && <PreviewBox imageUrl={previewImageUrl} />}
 
             {!isViewOnly && <PromptBox3D
               cameras={cameras}

frontend/libs/components/pagescene/src/lib/comps/AnonHintChip/AnonHintChip.tsx

@@ -0,0 +1,33 @@
+import { useContext } from "react";
+import { FontAwesomeIcon } from "@fortawesome/react-fontawesome";
+import { faArrowRightToBracket } from "@fortawesome/pro-solid-svg-icons";
+import { EngineContext } from "../../contexts/EngineContext/EngineContext";
+import { usePageSceneStore, useIsViewOnly } from "../../PageSceneStore";
+
+// Quiet "you're signed out" affordance shown in the editor playground for
+// anonymous visitors. Hidden in view-only mode (the visitor is consuming
+// someone else's scene; no upsell pressure needed). The actual per-action
+// signup CTAs (Save, Generate, Upload) still fire when the user clicks
+// those buttons — this chip just sets expectations up front.
+export const AnonHintChip = () => {
+  const editor = useContext(EngineContext);
+  const currentUserToken = usePageSceneStore((s) => s.currentUserToken);
+  const isViewOnly = useIsViewOnly();
+
+  if (currentUserToken || isViewOnly) return null;
+
+  const handleClick = () => {
+    editor?.adapter.promptSignup?.("hint");
+  };
+
+  return (
+    <button
+      type="button"
+      onClick={handleClick}
+      className="glass flex items-center gap-2 rounded-full border border-white/10 px-3 py-1.5 text-xs font-medium text-white/80 shadow-md transition-colors hover:bg-ui-controls/100 hover:text-white"
+    >
+      <FontAwesomeIcon icon={faArrowRightToBracket} className="opacity-70" />
+      Sign up to save
+    </button>
+  );
+};

frontend/libs/components/pagescene/src/lib/comps/AnonHintChip/index.ts

@@ -0,0 +1 @@
+export { AnonHintChip } from "./AnonHintChip";

frontend/libs/components/pagescene/src/lib/comps/Controls3D/Controls3D.tsx

@@ -14,7 +14,6 @@ import {
 import { ButtonIconSelect } from "@storyteller/ui-button-icon-select";
 import { Button } from "@storyteller/ui-button";
 import { Tooltip } from "@storyteller/ui-tooltip";
-import { SettingsModal } from "@storyteller/ui-settings-modal";
 import { PopoverMenu } from "@storyteller/ui-popover";
 import { FontAwesomeIcon } from "@fortawesome/react-fontawesome";
 import {
@@ -52,7 +51,6 @@ export const Controls3D = () => {
     })),
   );
   const [showEmptySceneTooltip, setShowEmptySceneTooltip] = useState(false);
-  const [isSettingsModalOpen, setIsSettingsModalOpen] = useState(false);
   const [upload3DIsShowing, setUpload3DIsShowing] = useState(false);
   const [isAddAssetPopoverOpen, setIsAddAssetPopoverOpen] = useState(false);
   const [uploadImageIsShowing, setUploadImageIsShowing] = useState(false);
@@ -306,13 +304,6 @@ export const Controls3D = () => {
 
       <AssetModal />
 
-      <SettingsModal
-        isOpen={isSettingsModalOpen}
-        onClose={() => setIsSettingsModalOpen(false)}
-        globalAccountLogoutCallback={() => editor?.adapter.performLogout()}
-        initialSection="accounts"
-      />
-
       {editor &&
         editor.adapter.renderAssetUploader({
           isOpen: upload3DIsShowing,

frontend/libs/components/pagescene/src/lib/comps/ControlsTopButtons/ControlsTopButtons.tsx

@@ -169,20 +169,26 @@ export const ControlsTopButtons = () => {
             {
               label: "Load my scene",
               description: "Ctrl+O",
-              dialogProps: {
-                title: "Load a Saved Scene",
-                content: (
-                  <LoadUserScenes onSceneSelect={handleSceneSelection} />
-                ),
-                confirmButtonProps: {
-                  label: "Load",
-                  disabled: sceneTokenSelected === "",
-                  onClick: handleButtonLoadScene,
-                },
-                closeButtonProps: { label: "Cancel" },
-                showClose: true,
-                className: "max-w-5xl",
-              },
+              ...(currentUserToken
+                ? {
+                    dialogProps: {
+                      title: "Load a Saved Scene",
+                      content: (
+                        <LoadUserScenes onSceneSelect={handleSceneSelection} />
+                      ),
+                      confirmButtonProps: {
+                        label: "Load",
+                        disabled: sceneTokenSelected === "",
+                        onClick: handleButtonLoadScene,
+                      },
+                      closeButtonProps: { label: "Cancel" },
+                      showClose: true,
+                      className: "max-w-5xl",
+                    },
+                  }
+                : {
+                    onClick: () => editor?.adapter.promptSignup?.("load"),
+                  }),
             },
             {
               disabled: !canSave,

frontend/libs/components/pagescene/src/lib/comps/PreviewBox/PreviewBox.tsx

@@ -0,0 +1,42 @@
+import { useState } from "react";
+import { FontAwesomeIcon } from "@fortawesome/react-fontawesome";
+import { faXmark } from "@fortawesome/pro-solid-svg-icons";
+
+// Small fixed-position card shown next to the camera in view-only mode.
+// Renders the author's generation result so a visitor can see what the
+// scene was made to produce. Today this is scaffolding only — the URL
+// data path (likely a new field returned by adapter.loadScene's response
+// payload, propagated into sceneMeta.previewImageUrl) is wired up in a
+// follow-up PR. Renders null when no URL is supplied, so it's safe to
+// mount unconditionally inside the isViewOnly branch.
+export interface PreviewBoxProps {
+  imageUrl?: string;
+}
+
+export const PreviewBox = ({ imageUrl }: PreviewBoxProps) => {
+  const [dismissed, setDismissed] = useState(false);
+
+  if (!imageUrl || dismissed) return null;
+
+  return (
+    <div className="glass absolute bottom-6 right-6 z-20 flex w-48 flex-col gap-2 rounded-lg border border-white/10 p-2 shadow-lg">
+      <button
+        type="button"
+        onClick={() => setDismissed(true)}
+        className="absolute right-1 top-1 flex h-5 w-5 items-center justify-center rounded-full text-white/60 hover:bg-white/10 hover:text-white"
+        aria-label="Hide preview"
+      >
+        <FontAwesomeIcon icon={faXmark} className="text-xs" />
+      </button>
+      <img
+        src={imageUrl}
+        crossOrigin="anonymous"
+        alt="Author's generation"
+        className="rounded-md"
+      />
+      <span className="text-center text-[11px] text-white/60">
+        Author's generation
+      </span>
+    </div>
+  );
+};

frontend/libs/components/pagescene/src/lib/comps/PreviewBox/index.ts

@@ -0,0 +1,2 @@
+export { PreviewBox } from "./PreviewBox";
+export type { PreviewBoxProps } from "./PreviewBox";