fix(#73): consume canonical Weekend Context contract and repair navigation

Address the independent review blockers on PR #80 after rebasing onto the
authoritative #72 Weekend Context API.

- Replace the invented frontend WeekendContext with the exact backend contract
  (temporal_state, previous/focus/next meetings, previous_completed/active/next/
  default_analysis sessions with availability). Every valid canonical payload now
  maps to a designed state via a total resolveViewState; a well-formed response
  can never fall through to the limited-data placeholder.
- Make the canonical read the single source of truth: useWeekendContext no longer
  fans out to season/meetings/per-weekend/OpenF1/live queries. Only supplementary
  championship + news reads run, and only once the canonical context resolves.
- Fix the Prepare/analysis flow: /preview is a stable alias that renders the
  preparation surface (PreSessionView) instead of redirecting back to the same
  between-races screen.
- One primary navigation system per breakpoint: the mobile top-bar links are
  hidden so the bottom bar is the sole primary nav, and Admin is moved out of
  every Primary landmark into an operator-utilities toolbar.
- Add Vitest coverage for the contract mapping, every temporal state, loading/
  error/limited surfaces, the no-fanout guarantee, the /preview CTA, and the nav
  hierarchy; add hermetic Playwright journeys (seeded + injected canonical
  payloads), 390/768/1440 overflow checks, and Weekend visual snapshots. Retire
  the stale Command Center specs/snapshots.

Co-authored-by: Cursor <cursoragent@cursor.com>

tests/production-smoke.spec.ts

@@ -3,11 +3,11 @@ import { test, expect } from '@playwright/test'
 const FULL_SESSION = 9472
 
 test.describe('Production serving (Go + built React)', () => {
-  test('serves command center as default route', async ({ page }) => {
+  test('serves the Weekend home as default route', async ({ page }) => {
     await page.goto('/')
 
-    await expect(page.getByTestId('command-center')).toBeVisible()
-    await expect(page.getByTestId('cc-session-9472')).toBeVisible()
+    await expect(page.getByTestId('weekend-page')).toBeVisible()
+    await expect(page.getByTestId('weekend-between-races')).toBeVisible()
   })
 
   test('serves race hub workspace from built assets', async ({ page }) => {
@@ -44,16 +44,21 @@ test.describe('Production serving (Go + built React)', () => {
     await expect(page.getByText('No live session active')).toBeVisible()
   })
 
-  test('nav links work from built SPA', async ({ page }) => {
+  test('primary nav links and Admin utility work from built SPA', async ({ page }) => {
     await page.goto('/')
-    await page.locator('.app-nav').getByRole('link', { name: 'Race Hub' }).click()
-    await expect(page).toHaveURL(/\/race-hub/)
+    const primary = page.getByRole('navigation', { name: 'Primary' }).first()
 
-    await page.locator('.app-nav').getByRole('link', { name: 'Admin', exact: true }).click()
+    await primary.getByRole('link', { name: 'Championship', exact: true }).click()
+    await expect(page).toHaveURL(/\/championship/)
+
+    await primary.getByRole('link', { name: 'Explore', exact: true }).click()
+    await expect(page).toHaveURL(/\/explore/)
+
+    await primary.getByRole('link', { name: 'Weekend', exact: true }).click()
+    await expect(page).toHaveURL('/')
+
+    // Admin is an operator utility outside the Primary landmark.
+    await page.getByRole('toolbar', { name: 'Operator utilities' }).getByRole('link', { name: 'Admin' }).click()
     await expect(page).toHaveURL(/\/admin/)
-
-    await page.getByRole('link', { name: 'Live', exact: true }).click()
-    await expect(page).toHaveURL(/\/live/)
-    await expect(page.getByTestId('live-empty')).toBeVisible()
   })
 })