Prep for the RC1 release of the desktop app

frontend/src/components/panels/Welcome.svelte

@@ -4,6 +4,7 @@
 	import type { Editor } from "@graphite/editor";
 	import type { Layout } from "@graphite/messages";
 	import { patchLayout, UpdateWelcomeScreenButtonsLayout } from "@graphite/messages";
+	import { isDesktop } from "@graphite/utility-functions/platform";
 	import { extractPixelData } from "@graphite/utility-functions/rasterization";
 
 	import LayoutCol from "@graphite/components/layout/LayoutCol.svelte";
@@ -72,13 +73,15 @@
 		</LayoutCol>
 	</LayoutCol>
 	<LayoutCol class="bottom-message">
-		{#if new Date().getFullYear() === 2025}
-			<TextLabel italic={true} disabled={true}>
+		<TextLabel italic={true} disabled={true}>
+			{#if isDesktop()}
+				You are testing Release Candidate 1 of the 1.0.0 desktop release. Please regularly check Discord for the next testing build and report issues you encounter.
+			{:else if new Date().getFullYear() === 2025}
 				September 2025 release — <a href="https://youtube.com/watch?v=Vl5BA4g3QXM" target="_blank">What's new? (video)</a>
 				— Note: some older documents may render differently and require manual fixes.
 				<a href="https://ec6796b4.graphite-editor.pages.dev/" target="_blank">Need the old version?</a>
-			</TextLabel>
-		{/if}
+			{/if}
+		</TextLabel>
 	</LayoutCol>
 </LayoutCol>