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/LiveHandoffView.tsx

@@ -1,40 +1,45 @@
 import { Link } from '@tanstack/react-router'
 import { ChevronRight, Radio } from 'lucide-react'
 import type { WeekendContext } from '../../types'
-import { EventPodium, Flag, SessionTimeline } from './shared'
+import { EventPodium, Flag, SessionRail, railNodes } from './shared'
+import { analysisSessionKey, meetingIdentity } from '../../lib/weekendContext'
 
 export function LiveHandoffView({ context }: { context: WeekendContext }) {
-  const { active_meeting_name, active_circuit_short_name, sessions, last_session } = context
-  const liveSession = sessions?.find((s) => s.status === 'live')
+  const focus = meetingIdentity(context.focus_meeting ?? context.active_session?.meeting)
+  const active = context.active_session?.session
+  const previous = context.previous_completed_session
+  const previousName = previous?.session.session_name ?? 'Last session'
+  const analysisKey = analysisSessionKey(context)
+  const nodes = railNodes(previous, context.active_session, context.next_session)
 
   return (
-    <div className="wk-live" data-testid="weekend-live" data-state={context.state}>
+    <div className="wk-live" data-testid="weekend-live" data-state="session_live">
       <div className="wk-eyebrow mono" data-testid="wk-eyebrow">Session live</div>
 
       <section className="wk-live-card" data-testid="wk-live-card">
         <div className="wk-live-head">
           <div className="wk-event-id">
-            <Flag code={context.last_event?.country_code} flag={context.last_event?.country_flag} />
-            <h1 className="wk-sessions-title">{active_meeting_name ?? 'Live session'}</h1>
+            <Flag code={focus?.country_code} flag={focus?.country_flag} />
+            <h1 className="wk-sessions-title">{focus?.meeting_name ?? 'Live session'}</h1>
           </div>
           <span className="wk-live-pulse" aria-hidden="true" />
         </div>
-        {active_circuit_short_name && <p className="wk-sessions-circuit mono">{active_circuit_short_name}</p>}
+        {focus?.circuit_short_name && <p className="wk-sessions-circuit mono">{focus.circuit_short_name}</p>}
         <p className="wk-live-lead">
-          {liveSession ? `${liveSession.session_name} is on track now.` : 'A session is running now.'}
+          {active?.session_name ? `${active.session_name} is on track now.` : 'A session is running now.'}
         </p>
         <Link to="/live" className="wk-cta wk-cta-primary wk-cta-wide" data-testid="wk-watch-live">
           <Radio size={15} aria-hidden="true" /> Watch live timing <ChevronRight size={15} aria-hidden="true" />
         </Link>
       </section>
 
-      {sessions && <SessionTimeline sessions={sessions} />}
+      <SessionRail nodes={nodes} />
 
-      {last_session && (
+      {previous && (
         <section className="wk-recap-card" data-testid="wk-last-session">
-          <span className="wk-recap-eyebrow mono">{last_session.label} · Complete</span>
-          <h2 className="wk-recap-title">What happened in {last_session.label}</h2>
-          <EventPodium event={last_session} />
+          <span className="wk-recap-eyebrow mono">{previousName} · Complete</span>
+          <h2 className="wk-recap-title">What happened in {previousName}</h2>
+          <EventPodium sessionKey={analysisKey} />
         </section>
       )}
     </div>