fix(app): hide badge for builtin slash commands

Add source: 'command' to builtin and config-defined commands so they
don't show a 'custom' badge. Only MCP and skill commands show badges.

packages/app/src/components/prompt-input.tsx

@@ -1728,7 +1728,7 @@ export const PromptInput: Component<PromptInputProps> = (props) => {
                         </Show>
                       </div>
                       <div class="flex items-center gap-2 shrink-0">
-                        <Show when={cmd.type === "custom"}>
+                        <Show when={cmd.type === "custom" && cmd.source !== "command"}>
                           <span class="text-11-regular text-text-subtle px-1.5 py-0.5 bg-surface-base rounded">
                             {cmd.source === "skill"
                               ? language.t("prompt.slash.badge.skill")