feat(multiday): Phase 2 polish — day tabs, per-day SEO/ICS/hours [tracking]

[BreakableHoodie]

Deferred from the Phase-1 epic. Do not start until Phase 1 is merged and proven.

Polish layered on the proven foundation:

• Sticky day headers/tabs + ?day=N URL anchor (ScheduleView, MySchedule).
• Per-day subEvent JSON-LD (functions/event/[slug].js) — validate with Google Rich Results Test; SEO regression risk.
• Day-aware ICS export — real per-set dates in functions/api/feeds/ical.js (coordinate with the fix(feeds): ICS calendar feed declares America/Los_Angeles timezone and a foreign UID domain #509 TZ fix already merged).
• Day-aware localStorage staleness + "today" filter (scheduleStorage.js, timeFilter.js).
• Optional: per-day venue hours/doors; activate the dead performances.stage column for multi-stage.

Scoping: #510.

[BreakableHoodie]

Design pass complete (2026-07-15). Full architecture blueprint produced; work split into 4 PRs, ordered by risk. Triage results:

Item	Status
Sticky day tabs + ?day=N	Not built → PR-3 (risk 5/10)
Per-day subEvent JSON-LD	Not built → PR-4 (risk 7/10, own PR + Google Rich Results validation gate)
Day-aware ICS export	Not built — live bug: ical.js never selects performance_date, every VEVENT gets the event start date → PR-2 (risk 3/10)
Day-aware localStorage staleness + "today" filter	Not built — live bug: saveSelectedBands callers pass date not end_date, so multi-day schedules go stale on day 2; also timeFilter.js "today" uses calendar midnight, not the 6 AM festival boundary → PR-1 (risk 2/10)
Per-day venue hours/doors	Already shipped end-to-end via #569 (storage doors_json 0052, validation, server+client start-edge gating, DayDivider/LiveContextBar display, EventFormModal admin editing). Closing this sub-item — nothing to build.
Activate dead performances.stage column	Column does not exist — grepped migrations 0001–0052 + setup-complete.sql, no stage anywhere and no code references. #510's claim was stale. Closing as inapplicable; if a real multi-stage-per-venue need appears, scope it fresh.

Two additional pre-existing bugs found during research, folded into PR-4 (both in functions/event/[slug].js, which PR-4 rewrites anyway): unannounced bands leak into crawler-facing JSON-LD on reveal-mode events (no reveal_mode gate, unlike schedule.js/ical.js/timeline.js — verified no reveal-mode events exist in prod today, so latent not active), and the JSON-LD startDate hardcodes -04:00 EDT year-round.

Build order: PR-1 → PR-2 (quiet correctness fixes first) → PR-3 (day tabs) → PR-4 (SEO-flagged JSON-LD, last, with pre-merge Rich Results gate + single-commit rollback plan). PR-1 and PR-2 are dispatched; PR-3 pending one product decision (does ?day=N filter the list or scroll-anchor to it).

[BreakableHoodie]

PR-3 (day tabs) merged (#636). Status of the tracking issue's five items:

• ✅ PR-1 day-aware staleness + Today filter — merged (fix: day-aware schedule staleness + festival-day Today filter #604)
• ✅ PR-2 day-aware ICS export — merged
• ✅ PR-3 sticky day tabs + ?day=N (FILTER model, Dre's call) — merged (feat: day-tab filter for multi-day event schedules (#542 PR-3) #636)
• ⏸️ PR-4 per-day subEvent JSON-LD — built + reviewed (feat: per-day subEvent JSON-LD for multi-day events (#542 PR-4) #634), held as DRAFT pending Dre's Google Rich Results Test (SEO gate); Vera caught + fixed the Google-required location field on subEvents pre-validation
• ✅ Per-day venue hours/doors — already shipped via feat: per-day doors/gates time — display it and gate "started" status on it #569 (closed as done)
• ✅ Dead performances.stage column — never existed (closed as inapplicable)

All buildable work complete. This tracking issue can close once #634's Rich Results validation passes and it merges. Follow-up #635 filed (venues query reveal_mode gate).