Restrict launches to prepared runtime images

src/lib/ui/components/NativeHostSelection.svelte

@@ -57,7 +57,7 @@
         </div>
     {/each}{/if}
     <p>Hosts keep the latest T5 and T6 files ready automatically. <a href="/game-files" target="_blank" rel="noopener">Upload game files</a> when they change. Existing servers keep their current files.</p>
-    <details><summary>Advanced: runtime override</summary><p>The configured default runtime is prepared automatically. Custom images must be prepared from the host page.</p><label>Plutainer runtime image<input required bind:value={selection.image} disabled={disabled} onchange={() => onchange?.()} /></label></details>
+    <details><summary>Advanced: runtime override</summary><p>The configured default runtime is prepared automatically. Custom images must first be prepared by an admin from the destination host page.</p><label>Plutainer runtime image<input required bind:value={selection.image} disabled={disabled} onchange={() => onchange?.()} /></label></details>
     {#if network}<details><summary>Network overrides</summary><label>Local bind address<input bind:value={selection.bindAddress} placeholder="Host default" disabled={disabled} onchange={() => onchange?.()} /></label><label>Public / NAT address<input bind:value={selection.publicAddress} placeholder="Host default" disabled={disabled} onchange={() => onchange?.()} /></label><label>Public / NAT port<input type="number" min="1" max="65535" bind:value={selection.publicPort} placeholder="Same as local port" disabled={disabled} onchange={() => onchange?.()} /></label><p>Public mapping does not change the local Docker port reservation.</p></details>{/if}
 </section>