fix(street-level): IC8 review of KartaView — cones on the right page, pano sizing

P1s from the correctness review, each with a regression test:
- Cones showed the wrong page of a long sequence (cache keyed by
  sequence; no re-centre after a close or a same-drive line click):
  KartaView always reselects, and re-centres whenever a photo of the
  selected sequence opens on another page.
- A 360° photo's first frame was one colour: the canvas was sized while
  hidden (1×1). It is shown first, and re-measured every frame.

P2/P3s: a storage timeout or 5xx is not remembered as archived (only
403/404/409/410 are); dense z13 tiles draw up to 1,600 lines (a third of
downtown Detroit was cut); decoded tiles are kept 10 min; a timed-out tile
is asked once more; pages are 250 photos and the newest page request goes
first; a photo far past deleted ones, or unlisted at a page edge, still
finds its neighbours; a step that gets no answer is not the end; a lost
WebGL context redraws the photo, and a failed one is retried on the next
mount; the first flat image comes from the proxy (KartaView's own can be
1.7 MB); fileurl fallbacks must be https storage hosts; oversized answers
are refused; keyboard (Shift+← →, ↑ ↓, + −) and pinch look around a
panorama; focus stays in the viewer when a step button disables. Docs:
share links with 0.m.0, keyless count, CURRENT-STATE matched to the code.

Co-Authored-By: Claude Opus 5.5 <[email protected]>

CHANGELOG.md

@@ -103,7 +103,7 @@
   look, wheel to zoom), with cones along its drive and ‹ › / ← → to step
   through it. The caption links to the full-size photo (KartaView's photo
   pages fail for signed-out visitors), and the globe credits "© KartaView
-  contributors, CC BY-SA 4.0". Share links carry it as `r.kartaview-1`.
+  contributors, CC BY-SA 4.0". Share links carry it as `0.m.0_0.r.kartaview-1`. Archived photos (KartaView answers 409) are skipped by the click and by ‹ ›; a keyboard and pinch look around a 360° photo.
   Mapillary's line coverage and sequence cones are now shared by both
   (`lineCoverage.js`, `sequenceCones.js`).