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]>

src/layers/streetLevel/registry.js

@@ -22,8 +22,8 @@ export function filtersOf(provider) {
  * @property {boolean} [defaultOn]     Default true.
  * @property {{kind: 'view-cone', color: string}} [marker]   Default: GEV's pin.
  * @property {Array<'pano'|'since'>} [filters]   Filters it honours (default both).
- * @property {{noun: string, action: string}} [coverageLabel]
- * @property {boolean} [highlightsSequence]   Its lines show the selected sequence (default true; the legend's "Selected" needs one).   How the panel counts its lines and says what a click does (default: sequences, "click a line for its photos").
+ * @property {{noun: string, action: string}} [coverageLabel]   How the panel counts its lines and says what a click does (default: sequences, "click a line for its photos").
+ * @property {boolean} [highlightsSequence]   Its lines show the selected sequence (default true; the legend's "Selected" needs one).
  * @property {(context: ProviderContext) => ProviderInstance} create
  *
  * @typedef {object} ProviderContext   Handed to `create()` once by the core.
@@ -67,6 +67,7 @@ export function filtersOf(provider) {
  * @property {() => void} resize
  * @property {(host: HTMLElement) => Promise<void>} [prewarm]
  * @property {(mode: 'letterbox'|'fill') => void} [setRenderMode]
+ * @property {() => boolean} [supportsRenderModes]   False while the image has no frame to fit (a panorama): FIT / FILL hide.
  * @property {(listener: (pose: StreetPose) => void) => () => void} onPose
  *
  * @typedef {object} StreetPose