feat(onboarding): detect UUID username and add completeProfile layout action

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

src/routes/(app)/+layout.server.ts

@@ -1,11 +1,45 @@
-import { redirect } from '@sveltejs/kit';
-import type { LayoutServerLoad } from './$types';
+import { redirect, fail } from '@sveltejs/kit';
+import { isErr, unwrapErr } from 'option-t/plain_result';
+import { zod, type ZodObjectType } from 'sveltekit-superforms/adapters';
+import { setError, superValidate } from 'sveltekit-superforms';
+import { patchUserUpdate } from '$lib/api';
+import { createApiClient } from '$lib/server/api';
+import { callSdk } from '$lib/server/errors';
+import { onboardingSchema } from '$lib/schemas/onboarding';
+import type { LayoutServerLoad, Actions } from './$types';
 
-export const load: LayoutServerLoad = ({ locals, url, cookies }) => {
+const UUID_RE = /^[0-9a-f]{8}-[0-9a-f]{4}-[0-9a-f]{4}-[0-9a-f]{4}-[0-9a-f]{12}$/i;
+
+// onboardingSchema fields are required strings but don't satisfy ZodObjectType's
+// Record<string,unknown> index signature — same cast pattern as profile page.
+const schema = onboardingSchema as unknown as ZodObjectType;
+
+export const load: LayoutServerLoad = async ({ locals, url, cookies }) => {
 	if (!locals.user) {
 		const redirectTo = encodeURIComponent(url.pathname + url.search);
 		throw redirect(303, `/app/authorize?redirect_to=${redirectTo}`);
 	}
 	const theme = (cookies.get('theme') as 'dark' | 'light') ?? 'dark';
-	return { user: locals.user, theme };
+	const needsOnboarding = UUID_RE.test(locals.user.username);
+	const onboardingForm = await superValidate(zod(schema));
+	return { user: locals.user, theme, needsOnboarding, onboardingForm };
+};
+
+export const actions: Actions = {
+	completeProfile: async (event) => {
+		const onboardingForm = await superValidate(event.request, zod(schema));
+		if (!onboardingForm.valid) return fail(400, { onboardingForm });
+		const api = createApiClient(event);
+		const result = await callSdk(() =>
+			patchUserUpdate({
+				client: api,
+				body: {
+					username: onboardingForm.data.username as string,
+					nickname: onboardingForm.data.nickname as string
+				}
+			})
+		);
+		if (isErr(result)) return setError(onboardingForm, '', unwrapErr(result).message);
+		return { onboardingForm };
+	}
 };