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/components/weekend/PreSessionView.tsx

@@ -2,31 +2,37 @@ import { Link } from '@tanstack/react-router'
 import { ChevronRight } from 'lucide-react'
 import type { WeekendContext } from '../../types'
 import { RacePreviewPage } from '../../pages/RacePreviewPage'
-import { CountdownDisplay, Flag, SeasonNavStrip, SessionTimeline } from './shared'
+import { ChampionshipRoundStrip, CountdownDisplay, Flag, SessionRail, railNodes } from './shared'
+import { meetingIdentity } from '../../lib/weekendContext'
 
 /**
  * PreSessionView folds the race preview surface into the Weekend home so there is
  * no separate Preview destination. It reuses the existing preview page content and
- * frames it with the next-session countdown and compact season navigation.
+ * frames it with the next-session countdown and compact season navigation. It also
+ * backs the /preview alias, so saved preview links resolve here instead of looping.
  */
 export function PreSessionView({ context, now }: { context: WeekendContext; now: Date }) {
-  const next = context.next_event
-  const nextStart = context.next_session?.date_start ?? next?.next_session_start ?? next?.date_start
+  const meeting = meetingIdentity(context.next_meeting ?? context.focus_meeting)
+  const next = context.next_session?.session
+  const nextStart = next?.date_start ?? meeting?.date_start
+  const nodes = railNodes(
+    context.previous_completed_session,
+    context.active_session,
+    context.next_session,
+  )
 
   return (
-    <div className="wk-pre" data-testid="weekend-pre-session" data-state={context.state}>
+    <div className="wk-pre" data-testid="weekend-pre-session" data-state="pre_session">
       <div className="wk-eyebrow mono" data-testid="wk-eyebrow">Pre-session</div>
 
-      {next && (
+      {meeting && (
         <header className="wk-pre-head" data-testid="wk-pre-head">
           <div className="wk-event-id">
-            <Flag code={next.country_code} flag={next.country_flag} />
-            <h1 className="wk-sessions-title">{next.meeting_name}</h1>
+            <Flag code={meeting.country_code} flag={meeting.country_flag} />
+            <h1 className="wk-sessions-title">{meeting.meeting_name}</h1>
           </div>
           <div className="wk-pre-countdown">
-            <span className="wk-next-label mono">
-              {context.next_session?.session_name ?? next.next_session_name ?? 'Next session'}
-            </span>
+            <span className="wk-next-label mono">{next?.session_name ?? 'Next session'}</span>
             <CountdownDisplay target={nextStart} now={now} />
           </div>
           <Link to="/live" className="wk-cta wk-cta-ghost" data-testid="wk-pre-live">
@@ -35,15 +41,16 @@ export function PreSessionView({ context, now }: { context: WeekendContext; now:
         </header>
       )}
 
-      {context.sessions && context.sessions.length > 0 && <SessionTimeline sessions={context.sessions} />}
+      {nodes.length > 0 && <SessionRail nodes={nodes} />}
 
       <div className="wk-pre-preview" data-testid="wk-pre-preview">
         <RacePreviewPage />
       </div>
 
-      {context.season_rounds && context.season_rounds.length > 0 && (
-        <SeasonNavStrip rounds={context.season_rounds} />
-      )}
+      <ChampionshipRoundStrip
+        round={context.championship_round}
+        total={context.total_championship_rounds}
+      />
     </div>
   )
 }