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>

frontend/src/pages/WeekendPage.tsx

@@ -4,24 +4,52 @@ import { BetweenSessionsView } from '../components/weekend/BetweenSessionsView'
 import { LiveHandoffView } from '../components/weekend/LiveHandoffView'
 import { PreSessionView } from '../components/weekend/PreSessionView'
 import { WeekendError, WeekendLimited, WeekendLoading } from '../components/weekend/StatusViews'
-import type { WeekendContext } from '../types'
+import { resolveViewState } from '../lib/weekendContext'
+import type {
+  WeekendBriefingItem,
+  WeekendChampionshipImpact,
+  WeekendContext,
+  WeekendViewState,
+} from '../types'
 import '../styles/weekend.css'
 
-function renderState(context: WeekendContext, now: Date) {
-  switch (context.state) {
-    case 'loading':
-      return <WeekendLoading />
-    case 'error':
-      return <WeekendError message={context.message} />
-    case 'limited_data':
-      return <WeekendLimited message={context.message} season={context.season} />
-    case 'between_races':
+interface RenderArgs {
+  context: WeekendContext
+  now: Date
+  championship?: WeekendChampionshipImpact
+  briefing: WeekendBriefingItem[]
+  /** When true (the /preview alias), foreground the preparation surface. */
+  preview: boolean
+}
+
+function renderState(view: WeekendViewState, args: RenderArgs) {
+  const { context, now, championship, briefing, preview } = args
+  // The /preview alias always resolves to the preparation surface as long as
+  // there is a next event to prepare for, regardless of the temporal state. This
+  // keeps saved /preview links and the "Prepare for …" CTA meaningful instead of
+  // redirecting straight back to the same between-races screen.
+  if (preview && context.next_meeting) {
+    return <PreSessionView context={context} now={now} />
+  }
+
+  switch (view) {
+    case 'no_season':
+      return <WeekendLimited season={context.season} />
+    case 'between_weekends':
     case 'post_weekend':
     case 'season_complete':
-      return <BetweenRacesView context={context} now={now} />
+      return (
+        <BetweenRacesView
+          context={context}
+          now={now}
+          view={view}
+          championship={championship}
+          briefing={briefing}
+        />
+      )
     case 'between_sessions':
     case 'session_settling':
-      return <BetweenSessionsView context={context} now={now} />
+      return <BetweenSessionsView context={context} now={now} view={view} briefing={briefing} />
     case 'session_live':
       return <LiveHandoffView context={context} />
     case 'pre_session':
@@ -31,12 +59,36 @@ function renderState(context: WeekendContext, now: Date) {
   }
 }
 
-export function WeekendPage() {
-  const { context, now } = useWeekendContext()
+export function WeekendPage({ preview = false }: { preview?: boolean }) {
+  const { context, loadState, error, championship, briefing, now } = useWeekendContext()
+
+  if (loadState === 'loading') {
+    return (
+      <main className="wk-page" data-testid="weekend-page" data-state="loading">
+        <WeekendLoading />
+      </main>
+    )
+  }
+
+  if (loadState === 'error' || context == null) {
+    return (
+      <main className="wk-page" data-testid="weekend-page" data-state="error">
+        <WeekendError message={error?.message} />
+      </main>
+    )
+  }
+
+  const view = resolveViewState(context)
 
   return (
-    <main className="wk-page" data-testid="weekend-page" data-state={context.state}>
-      {renderState(context, now)}
+    <main
+      className="wk-page"
+      data-testid="weekend-page"
+      data-state={view}
+      data-temporal-state={context.temporal_state}
+      data-preview={preview ? 'true' : undefined}
+    >
+      {renderState(view, { context, now, championship, briefing, preview })}
     </main>
   )
 }