test(e2e): smoke spec — app loads and OTC sign-in succeeds via Mailpit

The first end-to-end smoke spec, run live against the Tier-1 stack
(§22 M3-0 Task 7). Drives the §6.2 email OTC sign-in: loads the app,
requests a code, reads it from Mailpit, verifies it, and asserts the
verify returns ok:true and sets the rfc_session cookie.

Supporting harness fixes:
- Makefile: add .PHONY so `make e2e` actually runs (the e2e/ directory
  was shadowing the target, making it a no-op).
- mailpit.js: guard the per-message detail fetch (if !full.ok continue)
  and scan the plain-text part before HTML so the \d{6} match can't
  latch onto a stray number.
- spec uses a unique per-run email to avoid the per-email request
  cooldown (OTC_REQUEST_COOLDOWN_SECONDS) on re-runs.

Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>

e2e/smoke.spec.js

@@ -0,0 +1,48 @@
+import { test, expect } from '@playwright/test'
+import { waitForLatestOtc, clearMailpit } from './lib/mailpit.js'
+
+// Unique per-run address. The §6.2 request path enforces a per-email
+// cooldown (OTC_REQUEST_COOLDOWN_SECONDS, default 60s), so a fixed
+// address would 429 on any re-run inside the window. A fresh address per
+// run sidesteps that without touching backend config.
+const EMAIL = `e2e-${Date.now()}-${Math.floor(Math.random() * 1e6)}@example.test`
+
+// First end-to-end smoke spec (M3-0 Task 7). Validates the whole Tier-1
+// harness: the web tier serves the app, the backend's OTC sign-in path
+// (§6.2) issues a code, Mailpit captures the outbound mail, and a verify
+// of that code succeeds and mints a session.
+//
+// No precondition/provisioning step is needed: the §6.2 OTC path admits
+// any syntactically-valid email and provisions a fresh `pending` user on
+// verify (see backend/app/otc.py). Turnstile is open in this stack
+// (TURNSTILE_REQUIRED=false, no secret), so the request body carries only
+// the email.
+test('app loads and an OTC sign-in succeeds', async ({ page, request }) => {
+  await clearMailpit()
+
+  await page.goto('/')
+  await expect(page).toHaveTitle(/.+/)
+
+  const reqRes = await request.post('/auth/otc/request', {
+    data: { email: EMAIL },
+  })
+  expect(reqRes.ok()).toBeTruthy()
+
+  const code = await waitForLatestOtc(EMAIL)
+  expect(code).toMatch(/^\d{6}$/)
+
+  const verifyRes = await request.post('/auth/otc/verify', {
+    data: { email: EMAIL, code },
+  })
+  expect(verifyRes.ok()).toBeTruthy()
+
+  // Prove the sign-in actually took: the verify handler returns ok:true
+  // and sets the `rfc_session` session cookie (§ SessionMiddleware,
+  // backend/app/main.py). Asserting the cookie — not brittle UI text —
+  // is what distinguishes a real sign-in from a bare 2xx.
+  const verifyBody = await verifyRes.json()
+  expect(verifyBody.ok).toBe(true)
+
+  const setCookie = verifyRes.headers()['set-cookie'] || ''
+  expect(setCookie).toContain('rfc_session=')
+})