test: E2E specs for signup, fight replay, and leaderboard flows

Bot registration (3 tests), human registration (1 test), fight replay
(2 tests for JS error checking), and leaderboard (3 tests for rendering).
All use Playwright with text-based selectors.

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

e2e/signup-human.spec.ts

@@ -0,0 +1,17 @@
+import { test, expect } from '@playwright/test'
+
+test.describe('human registration flow', () => {
+  test('select human mode shows avatar picker', async ({ page }) => {
+    await page.goto('/join')
+
+    // Generate identity
+    await page.getByText(/generate new identity/i).click()
+    await expect(page.getByText(/I FIGHT MYSELF/i)).toBeVisible({ timeout: 5_000 })
+
+    // Choose human mode
+    await page.getByText(/I FIGHT MYSELF/i).click()
+
+    // Should show human avatar picker
+    await expect(page.getByText(/pick.*avatar/i).first()).toBeVisible({ timeout: 5_000 })
+  })
+})