Please address the comments from this code review:

## Overall Comments
- In `ExaggeratedElevationLayer.fetchTile`, returning an empty object when `_elevation` is undefined can hide loading issues and produce invalid data; consider awaiting the layer load or throwing/logging an explicit error instead of returning a dummy tile.
- The `ExaggeratedElevationLayer` constructor always overrides `multiplier` from its first parameter and ignores any `multiplier` that might be passed via `properties`; if this class is ever instantiated by the ArcGIS runtime or via JSON, you may want to derive `multiplier` from `properties` to avoid surprising behavior.

## Individual Comments

### Comment 1
<location> `apps/fxc-front/src/app/components/3d/map3d-element.ts:472-478` </location>
<code_context>
-  const layer = new Layer();
-  layer.multiplier = multiplier;
-  return layer;
+  async fetchTile(
+    level: number,
+    row: number,
+    col: number,
+    options?: __esri.BaseElevationLayerFetchTileOptions,
+  ): Promise<__esri.ElevationTileData> {
+    if (!this._elevation) {
+      return {} as any;
+    }
</code_context>

<issue_to_address>
**issue (bug_risk):** Avoid returning an empty object when `_elevation` is not yet initialized.

Casting `{}` to `any` when `_elevation` is undefined breaks the contract of returning a valid `ElevationTileData` and can cause subtle runtime errors if `fetchTile` is called before `load` completes. Instead, either wait for initialization (e.g., `if (!this._elevation) await this.load();`) or throw a clear error so callers never receive an invalid tile payload.
</issue_to_address>

### Comment 2
<location> `apps/fxc-front/src/app/components/3d/map3d-element.ts:458-460` </location>
<code_context>
-          return data;
-        });
-      },
+  constructor(multiplier: number, properties?: __esri.BaseElevationLayerProperties | undefined) {
+    super(properties);
+    this.multiplier = multiplier;
+  }
+
</code_context>

<issue_to_address>
**suggestion (bug_risk):** Custom constructor signature may diverge from the standard ArcGIS layer construction pattern.

The current signature `(multiplier: number, properties?)` only forwards `properties` to `super` and relies on positional args, which diverges from the usual `new Layer({ ...properties })` pattern. This risks misuse if the layer is ever instantiated via standard ArcGIS mechanisms or elsewhere with `new ExaggeratedElevationLayer({ multiplier: 2 })`, where `multiplier` would be ignored.

Consider accepting a single `properties` object that includes `multiplier`:

```ts
constructor(properties?: __esri.BaseElevationLayerProperties & { multiplier?: number }) {
  super(properties);
  if (properties?.multiplier != null) {
    this.multiplier = properties.multiplier;
  }
}
```

and update call sites to `new ExaggeratedElevationLayer({ multiplier: this.multiplier })` to match the standard pattern.

Suggested implementation:

```typescript
  constructor(
    properties?: __esri.BaseElevationLayerProperties & { multiplier?: number },
  ) {
    super(properties);
    if (properties?.multiplier != null) {
      this.multiplier = properties.multiplier;
    }
  }


```

You will also need to update all instantiations of `ExaggeratedElevationLayer` in this file (and elsewhere in the codebase) to follow the standard ArcGIS pattern. For example, change:

```ts
new ExaggeratedElevationLayer(this.multiplier)
```

to:

```ts
new ExaggeratedElevationLayer({ multiplier: this.multiplier })
```

and if there were existing properties:

```ts
new ExaggeratedElevationLayer(this.multiplier, { id: 'exaggerated-elev' })
```

to:

```ts
new ExaggeratedElevationLayer({ id: 'exaggerated-elev', multiplier: this.multiplier })
```

Search for `new ExaggeratedElevationLayer(` and adjust each call accordingly so the first (and only) argument is a single properties object that may include `multiplier`.
</issue_to_address>