feat(fase-10): sidebar "+ New collective" entry + modal (10.6)

Adds a new "+ New collective" entry at the bottom of the sidebar
collective-switcher dropdown (and the mobile drawer for parity).
Clicking it opens a CreateCollectiveModal that reuses the same
onboarding form — name + emoji grid — and calls the existing
create_collective() RPC (migration 012). On success, the new
collective is appended to $userCollectives, set active in
$currentCollective, persisted to localStorage, and the user is sent
to /lists.

Side effects:
- Switcher now opens even with a single collective (previously gated
  on >1) so the entry is always reachable; the chevron is always
  shown.
- DesktopSidebar gets a data-testid on the switcher button so the
  Playwright suite can target it without text matching.

O-04 (rescued from Fase 7): Eva creates her first collective via
onboarding, then opens the switcher and creates a second one without
leaving /lists; both collectives end up in the switcher and the DB.

Co-Authored-By: Claude Opus 4.7 <noreply@anthropic.com>

apps/web/tests/e2e/sidebar-create-collective.test.ts

@@ -0,0 +1,65 @@
+/**
+ * O-04 (rescued from Fase 7) — sidebar "+ New collective" entry (Fase 10.6).
+ *
+ * Eva starts onboarded with one collective; she opens the sidebar switcher,
+ * clicks "+ New collective", fills the modal, and ends up on /lists with
+ * both collectives visible in the switcher.
+ */
+import { test, expect } from '@playwright/test';
+import { USERS } from '../fixtures/users.js';
+import { loginAs } from '../fixtures/login.js';
+import { resetEva } from '../fixtures/db.js';
+import { closePool, sql } from '@colectivo/test-utils';
+
+test.describe.configure({ mode: 'serial' });
+
+test.describe('Sidebar create collective (CU-H02 follow-up)', () => {
+	test.beforeEach(async () => {
+		await resetEva();
+	});
+
+	test.afterAll(async () => {
+		await resetEva();
+		await closePool();
+	});
+
+	test('O-04: Eva with one collective creates a second from the sidebar', async ({ page }) => {
+		// Onboard Eva with a first collective so the switcher renders.
+		const firstName = `Eva First ${Date.now()}`;
+		await loginAs(page, USERS.eva, { waitForCollective: false });
+		await expect(page).toHaveURL(/\/onboarding$/, { timeout: 15_000 });
+		await page.getByTestId('collective-name-input').fill(firstName);
+		await page.getByTestId('collective-submit').click();
+		await expect(page).toHaveURL(/\/lists$/, { timeout: 15_000 });
+
+		// Open the sidebar switcher and pick "+ New collective".
+		await page.getByTestId('sidebar-collective-switcher').click();
+		const newEntry = page.getByTestId('sidebar-create-collective');
+		await expect(newEntry).toBeVisible({ timeout: 5_000 });
+		await newEntry.click();
+
+		const secondName = `Eva Second ${Date.now()}`;
+		await page.getByTestId('create-collective-modal-name').fill(secondName);
+		await page.getByTestId('create-collective-modal-submit').click();
+
+		// Landed on /lists with the second collective active.
+		await expect(page).toHaveURL(/\/lists$/, { timeout: 15_000 });
+
+		// Both collectives in the switcher. Use .first() because the switcher
+		// header also renders the active collective name.
+		await page.getByTestId('sidebar-collective-switcher').click();
+		await expect(
+			page.getByTestId('desktop-sidebar').getByText(firstName).first()
+		).toBeVisible({ timeout: 5_000 });
+		await expect(
+			page.getByTestId('desktop-sidebar').getByText(secondName).first()
+		).toBeVisible();
+
+		// DB-side: Eva has two collectives.
+		const r = await sql(
+			'SELECT count(*)::int AS n FROM public.collectives WHERE created_by = $1',
+			[USERS.eva.id]
+		);
+		expect(r.rows[0].n).toBe(2);
+	});
+});