✨ feat(server): /api/info aggregator + frontend version footer

Sprint 2 of autonomous trainer day 2026-05-05. Mistral-implemented
through ICM workspace ship-info-aggregator (bootstrapped backend +
BDD before hitting price limit at stage 02), Claude-completed for
frontend + Playwright + verifier + PR.

Backend:
- GET /api/info aggregator returning version, commit_short, build_date,
  uptime_seconds, cache_enabled, healthz_status (single round trip)
- Optional cache via existing cache service (X-Cache: HIT/MISS)
- BDD scenario @critical covers happy path + version regex; cache
  scenario kept under @skip @bdd-deferred until BDD harness gains a
  cache-enabled mode

Frontend:
- AppFooterView (dumb) + AppFooter (smart wrapper, useFetch) following
  the HealthDashboard / HealthDashboardView pattern
- layouts/default.vue auto-applied via NuxtLayout in app.vue
- humaniseUptime helper in utils/
- Playwright tests use route.fulfill mocking (decoupled from dev-proxy
  infra), assert visible AND content (PR #32 lesson)

Docs:
- documentation/API.md /api/info entry with schema and rationale
- ADR-0026 documents composite endpoint vs separate calls choice

Verifier verdict (skill-driven, audit at stage 04): APPROVE_WITH_NITS.
Nits: handleInfo is 51 lines (could split into builder + emitter);
X-Cache: DISABLED could improve ops clarity.

Out-of-scope follow-up: existing tests/e2e/health.spec.ts happy path
hits the same dev-proxy infra issue as my footer happy path before
mocking. Same fix (server: false + route.fulfill) would apply.

frontend/tests/e2e/app-footer.spec.ts

@@ -0,0 +1,67 @@
+import { test, expect } from '@playwright/test'
+
+// Both specs mock /api/info so they decouple from the dev-proxy plumbing.
+// The integration with the real backend is covered by the BDD scenario in
+// features/info/info.feature (server-side, no frontend proxy in the loop).
+
+test('home page footer shows version, commit and uptime', async ({ page }) => {
+  await page.route('**/api/info', (route) => {
+    route.fulfill({
+      status: 200,
+      contentType: 'application/json',
+      body: JSON.stringify({
+        version: '1.4.0',
+        commit_short: '4a3f1bb',
+        build_date: '2026-05-05T00:00:00Z',
+        uptime_seconds: 8042,
+        cache_enabled: true,
+        healthz_status: 'healthy',
+      }),
+    })
+  })
+  await page.goto('/')
+
+  // Footer is mounted globally via layouts/default.vue
+  await expect(page.getByTestId('app-footer')).toBeVisible()
+
+  // The PR #32 lesson: assert content, not just visibility.
+  // Without the regex check the test would PASS even if the footer rendered the
+  // pending placeholder ("v?") indefinitely.
+  await expect(page.getByTestId('app-footer-info')).toBeVisible()
+  const versionLocator = page.getByTestId('app-footer-version')
+  await expect(versionLocator).toBeVisible()
+  await expect(versionLocator).toHaveText(/^v\d+\.\d+\.\d+$/)
+
+  // Commit and uptime should be present and non-empty.
+  await expect(page.getByTestId('app-footer-commit')).not.toBeEmpty()
+  await expect(page.getByTestId('app-footer-uptime')).not.toBeEmpty()
+
+  await page.screenshot({
+    path: 'tests/e2e/screenshots/app-footer-shows-version-commit-uptime.png',
+    fullPage: true,
+  })
+})
+
+// Regression spec: documents the expected error UX so we don't ship a silent failure.
+// Routes /api/info to a 502 mock so the test is reproducible regardless of backend.
+test('home page footer surfaces info endpoint errors gracefully', async ({ page }) => {
+  await page.route('**/api/info', (route) => {
+    route.fulfill({
+      status: 502,
+      contentType: 'application/json',
+      body: JSON.stringify({ error: 'simulated_backend_down' }),
+    })
+  })
+  await page.goto('/')
+
+  // Footer must NOT crash the page
+  await expect(page.getByTestId('app-footer')).toBeVisible()
+  await expect(page.getByTestId('app-footer-error')).toBeVisible()
+  // The error placeholder should NOT contain a real version pattern
+  await expect(page.getByTestId('app-footer-info')).not.toBeVisible()
+
+  await page.screenshot({
+    path: 'tests/e2e/screenshots/app-footer-surfaces-info-endpoint-errors-gracefully.png',
+    fullPage: true,
+  })
+})