status: six buckets for gig day, and the page stops inventing a doors time

Rebuilt against tonight's findings. Buckets Corpus/Audio/Surface become
Rig/Perf/Mix, which is what the night actually produced; Set 100%, Rehearsal
35% (six of seventeen, moved up from last), Rig/Perf/Mix gated on one pair of
hands, Observability 90%. Timeline is three stops, all today. Counters compute
from the clock and repaint every 60s.

The part worth keeping: no clock time appears on this page except the sourced
17:00. The previous version said doors at 19:00 and a rebuild changed it to
18:00 by reasoning from 'end of talks -> doors'. Both were guesses. There is no
entry for this gig in Perso/www/content/lives/2026 -- the canonical home for
venue, title, lineup and times -- and TODO_GIG.md never states one, so the rule
applies: never invent gig metadata, ask. The set now reads 'time tbc' and every
countdown anchors on the sound test.

That is enforced mechanically rather than by intention: the page's silent
self-test sweeps every derived string at 30-minute steps from 15 Sept to 5 Oct
and FAILS on any clock time that is not 17:00. Guessing a doors time back in
now breaks a test instead of quietly misinforming him at a glance. The two old
guesses survive only inside the comment that explains why they were wrong.

Verified: 420px frame -> scrollWidth 405 (no horizontal scroll), 1440px -> 3+3
grid with no orphan card, self-test PASS and silent, zero external requests,
HTTP 200 over localhost.