feat(race-hub): trustworthy defaults and fan-facing analysis hierarchy (#75)

Make bare /race-hub resolve to a completed session and never open empty
post-session analysis for a future race.

- Backend: add `default_analysis_session` to the Weekend context. It never
  resolves to a future session (picks the richest completed session, ties
  toward the later one; 0 when everything is upcoming). Existing
  `default_session_key` and deep links are unchanged.
- Frontend default resolution prefers the most recently completed weekend
  (`pickAnalysisFocusMeeting`) and consumes `default_analysis_session`, falling
  back to the switcher when only upcoming sessions exist.
- New `sessionState` lib maps timing + coverage to user language
  (upcoming/live/preparing/partial/ready/cancelled); the session rail, active
  sub-bar, and WeekendSwitcher now label states instead of raw x/11 counts.
- Future sessions render a purpose-built PreSessionView (expected availability +
  countdown) instead of empty Winner/Podium/Pole/Strategy/Compare cards.
- Analysis navigation regrouped into Story / Analysis / Data & Context; every
  existing tab is preserved. Diagnostics (renamed from Data Status) is now a
  secondary action and the raw dataset strip is hidden behind an explicit
  toggle, so operational coverage no longer precedes fan content.
- Loading/error states offer Retry and a path back to Weekend.

Tests: Go query tests for future-exclusion; Vitest for default selection,
future pre-session, partial state, error/retry, grouped nav, and sessionState;
hermetic Playwright for bare/completed/future/return-to-Weekend; new
race-hub-future visual snapshots. Seed adds a far-future session inside the
Monaco meeting (kept in-meeting so Command Center focus is unaffected).

Note: `default_analysis_session` is an additive field on the existing
`/weekend` contract (no new endpoint), per the spec's "context contract" scope.

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

internal/query/query_test.go

@@ -5,6 +5,7 @@ import (
 	"errors"
 	"path/filepath"
 	"testing"
+	"time"
 
 	"github.com/AmanTahiliani/box-box/internal/models"
 	"github.com/AmanTahiliani/box-box/internal/store"
@@ -376,6 +377,88 @@ func TestGetWeekendWithSessions(t *testing.T) {
 	}
 }
 
+func TestPickDefaultAnalysisSessionSkipsFuture(t *testing.T) {
+	now := mustTime(t, "2025-05-24T18:00:00Z")
+	sessions := []WeekendSession{
+		{ // completed qualifying, partial coverage
+			Session:  models.Session{SessionKey: 100, DateStart: "2025-05-24T14:00:00+00:00"},
+			Datasets: map[string]DatasetInfo{"results": availableLocal(1)},
+		},
+		{ // future race with the richest coverage — must NOT be selected
+			Session: models.Session{SessionKey: 200, DateStart: "2025-05-25T13:00:00+00:00"},
+			Datasets: map[string]DatasetInfo{
+				"results": availableLocal(1),
+				"laps":    availableLocal(1),
+				"stints":  availableLocal(1),
+			},
+		},
+	}
+
+	got := pickDefaultAnalysisSession(sessions, now)
+	if got != 100 {
+		t.Fatalf("pickDefaultAnalysisSession() = %d, want 100 (never a future session)", got)
+	}
+}
+
+func TestPickDefaultAnalysisSessionAllFuture(t *testing.T) {
+	now := mustTime(t, "2025-05-20T00:00:00Z")
+	sessions := []WeekendSession{
+		{Session: models.Session{SessionKey: 100, DateStart: "2025-05-24T14:00:00+00:00"}},
+		{Session: models.Session{SessionKey: 200, DateStart: "2025-05-25T13:00:00+00:00"}},
+	}
+
+	if got := pickDefaultAnalysisSession(sessions, now); got != 0 {
+		t.Fatalf("pickDefaultAnalysisSession() = %d, want 0 (everything upcoming)", got)
+	}
+}
+
+func TestPickDefaultAnalysisSessionPrefersRichestCompleted(t *testing.T) {
+	now := mustTime(t, "2025-05-26T00:00:00Z")
+	sessions := []WeekendSession{
+		{
+			Session:  models.Session{SessionKey: 100, DateStart: "2025-05-24T14:00:00+00:00"},
+			Datasets: map[string]DatasetInfo{"results": availableLocal(1)},
+		},
+		{
+			Session: models.Session{SessionKey: 200, DateStart: "2025-05-25T13:00:00+00:00"},
+			Datasets: map[string]DatasetInfo{
+				"results": availableLocal(1),
+				"laps":    availableLocal(1),
+			},
+		},
+	}
+
+	if got := pickDefaultAnalysisSession(sessions, now); got != 200 {
+		t.Fatalf("pickDefaultAnalysisSession() = %d, want 200 (richest completed)", got)
+	}
+}
+
+func TestGetWeekendSetsDefaultAnalysisSession(t *testing.T) {
+	prev := weekendNow
+	weekendNow = func() time.Time { return mustTime(t, "2025-05-26T00:00:00Z") }
+	t.Cleanup(func() { weekendNow = prev })
+
+	svc := openTestService(t)
+	seedRaceHubData(t, svc.store)
+
+	weekend, err := svc.GetWeekend(1229)
+	if err != nil {
+		t.Fatalf("GetWeekend() error = %v", err)
+	}
+	if weekend.DefaultAnalysisSession != 9472 {
+		t.Fatalf("DefaultAnalysisSession = %d, want 9472", weekend.DefaultAnalysisSession)
+	}
+}
+
+func mustTime(t *testing.T, value string) time.Time {
+	t.Helper()
+	parsed, err := time.Parse(time.RFC3339, value)
+	if err != nil {
+		t.Fatalf("parse time %q: %v", value, err)
+	}
+	return parsed
+}
+
 func TestGetChampionshipInputsIncludesSprintPoints(t *testing.T) {
 	// Regression for #57: Race-only aggregation dropped Sprint points.
 	// Setup: same meeting 1229 has Race (9472) 25pts + Sprint (9473) 8pts => total 33.