Festival phase: Live — now / next

[chiptus]

Parent

Epic #126 — Festival phases. PRD: docs/prd/festival-phases/2-live-phase.md.

What to build

When the edition is Live (useFestivalPhase() === "live", from #136), adapt the experience for someone standing in the field: they want what's on now and next, not a voting list. Live is an emphasis shift, not a different app — voting stays fully available and nothing from Planning is removed.

• Land on the Schedule tab by default — extend the phase-driven default-tab mechanism from Festival phase: Pre-Schedule & Planning experience #137 so Live → Schedule. No tabs added or hidden.
• New pure now/next classifier — (sets, now) → classification (now-playing / next / later-past), festival-tz, now injected. Mirrors the pure/injectable shape of getFestivalPhase. Reuses set timing already loaded for the Schedule and the timeUtils festival-tz helpers.
  • now-playing: time_start <= now < time_end (exactly at time_end ⇒ no longer now-playing).
  • next: the nearest upcoming set(s) after now; ties and multi-stage concurrency handled deterministically.
• Schedule-tab "Now / Next" section — when Live, lead with a section built from the classifier, above the existing full views (Timeline/List, or Multi-mode Schedule tab UX for days/stages reveal levels #47's progressive views below full). Now-playing marked as current; the next block shows immediately upcoming sets. Reuse the existing masked set row (MobileSetCard/set-row) so voting, set-detail links, and self-hiding stage/time badges come for free.
• Compact Live banner — reuse the shared phase-banner component with Live copy ("the festival is on"). One line.
• Sub-full reveal fallback — "Now / Next" needs time_start/time_end (only present at reveal level full). If Live is reached below full, skip the Now/Next section and show whatever the reveal level renders plus the Live banner. Never fabricate or leak hidden times.
• No live ticker — computed per render/navigation; no background timer.

Acceptance criteria

• When the edition is Live, the app lands on the Schedule tab by default.
• The now/next classifier marks a set now-playing for now in [time_start, time_end) and not at exactly time_end; selects nearest upcoming set(s) as "next"; handles ties / multi-stage concurrency deterministically; excludes missing/masked-time sets without error.
• Classifier is a standalone pure function unit-tested with now injected in a non-UTC festival timezone (incl. a viewer-vs-festival calendar-day mismatch); no clock/DOM/React mocking.
• The Schedule tab, when Live, leads with a Now / Next section above the full schedule, using the shared masked set row; the full schedule remains reachable.
• Compact Live banner shown, reusing the shared phase-banner component.
• Below reveal level full, the Now/Next section is skipped gracefully (banner still shown, no leaked times).

Blocked by

• Festival phase: Pre-Schedule & Planning experience #137 — Pre-Schedule & Planning experience (shared phase-banner component + phase-driven default-tab mechanism), which itself depends on Festival phase: derivation core + useFestivalPhase hook #136.