Merge origin/main: Google Street View, KartaView and Panoramax on the slim Street Level

Main gained three imagery providers (Google Street View, KartaView,
Panoramax), shared line-coverage, cone and photo-viewer modules, one source
lit at a time and the translated interface. Their shared modules still
carried what this branch removes, so the merge ports them onto it:

- lineCoverage.js is this branch's coverage.js made provider-neutral
  (draped lines near the ground only, the selection drawn over them, key
  and rate-limit blocking); sequenceCones.js is sequences.js the same way.
  Mapillary, KartaView and Panoramax all build on them; Mapillary moves
  back to providers/mapillary/ beside the others.
- No ground casting, mesh sampling, surface modes, FOLLOW, legend, prewarm,
  orbit overview points (Panoramax's density dots included), stale-tile
  swaps or water-filled point budget come back.
- Kept from main because the new providers need them: requiresMapStack and
  attachMapStackController (Street View on Google 3D only), ground clicks,
  openNearest with an optional provider nearestImage, openImage {frame},
  reportError, the view-cone marker (now an SVG glyph), filters /
  coverageLabel / sinceBasis, OPEN STREET VIEW, keyAlternatives and i18n.
- photoViewer.js treats the viewer as expanded when its wrap is full screen
  or the iPhone popover, as EXPAND now is.
- The fixture browser gate keeps its 8 steps and adds one each for
  KartaView and Panoramax; catalogs, docs, boundaries and format scope
  follow.

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

src/ui/styles/street-level.css

@@ -2,6 +2,12 @@
    The rail owns position and width (layers.css). */
 #street-level-panel {
   --sl-green: #05cb63;
+  /* KartaView's purple for lines; a lighter one where it is text (WCAG AA). */
+  --sl-kartaview: #635bff;
+  --sl-kartaview-text: #8f8aff;
+  /* Panoramax's orange; the darker one sits behind white text. */
+  --sl-panoramax: #ff6f00;
+  --sl-panoramax-fill: #b84e00;
   --sl-text: 0.6rem;
 }
 
@@ -151,6 +157,11 @@
   );
 }
 
+/* #635bff text on its own tint is 3.7:1 at this size; the lighter one is ~6:1. */
+.sl-chips .data-toggle-chip.active[data-chip-id='kartaview'] {
+  color: var(--sl-kartaview-text);
+}
+
 .sl-chips .data-toggle-chip.active::before {
   opacity: 1;
 }
@@ -160,6 +171,41 @@
   border-color: rgba(255, 179, 0, 0.55);
 }
 
+/* The coverage hint and OPEN STREET VIEW share a line; the hint wraps. */
+.sl-meta-row {
+  display: flex;
+  align-items: center;
+  gap: 8px;
+}
+
+.sl-meta-row .sl-meta {
+  flex: 1 1 auto;
+  min-width: 0;
+}
+
+/* Scoped to outrank .scene-btn's flex: 1, which squeezed the button to its
+   min-width beside a long coverage line and clipped its one-line label. */
+.sl-meta-row .sl-nearest-btn {
+  flex: 0 0 auto;
+}
+
+.sl-nearest-btn[hidden] {
+  display: none;
+}
+
+/* When the hint and the button do not both fit, the button takes its own line. */
+html:not([lang='en']) .sl-meta-row {
+  flex-wrap: wrap;
+}
+
+html:not([lang='en']) .sl-meta-row .sl-meta {
+  flex: 1 1 14em;
+}
+
+html:not([lang='en']) .sl-meta-row .sl-nearest-btn {
+  flex: 1 0 auto;
+}
+
 /* ── Errors ──────────────────────────────────────────────────────────────── */
 .sl-error {
   font-family: var(--font-sans);
@@ -184,6 +230,13 @@
   border-radius: 999px;
 }
 
+.sl-seg[hidden],
+.sl-controls[hidden],
+.sl-filters[hidden],
+.sl-since[hidden] {
+  display: none;
+}
+
 .sl-seg-btn {
   font-family: var(--font-mono);
   font-size: var(--sl-text);
@@ -238,6 +291,17 @@
   outline-offset: 3px;
 }
 
+.sl-since-note {
+  grid-column: 2;
+  font-family: var(--font-mono);
+  font-size: var(--sl-text-small);
+  color: var(--text-secondary);
+}
+
+.sl-since-note[hidden] {
+  display: none;
+}
+
 .sl-since-label {
   grid-column: 2;
   font-family: var(--font-mono);
@@ -461,6 +525,107 @@
   aspect-ratio: auto;
 }
 
+/* ── Photo viewer (KartaView, Panoramax) ─────────────────────────────────── */
+.sl-photo-viewer {
+  /* The lit source's colour: a focus ring, and behind the white ‹ › glyphs. */
+  --sl-photo-ring: var(--sl-kartaview-text);
+  --sl-photo-fill: color-mix(in srgb, var(--sl-kartaview) 85%, transparent);
+  position: absolute;
+  inset: 0;
+  background: #000;
+  outline: none;
+  overflow: hidden;
+}
+
+.sl-photo-viewer:focus-visible {
+  outline: none;
+}
+
+/* The photo and canvas fill the viewer and would cover a ring drawn on it:
+   draw the ring on a layer above them (clicks pass through). */
+.sl-photo-viewer:focus-visible::after {
+  content: '';
+  position: absolute;
+  inset: 0;
+  z-index: 3;
+  border: 2px solid var(--sl-photo-ring);
+  pointer-events: none;
+}
+
+/* White on #ff6f00 is 2.8:1; on the darker orange behind ‹ › it is 5.1:1. */
+.sl-photo-viewer[data-provider='panoramax'] {
+  --sl-photo-ring: var(--sl-panoramax);
+  --sl-photo-fill: var(--sl-panoramax-fill);
+}
+
+.sl-photo-flat,
+.sl-photo-pano {
+  position: absolute;
+  inset: 0;
+  width: 100%;
+  height: 100%;
+  user-select: none;
+}
+
+.sl-photo-flat {
+  object-fit: contain;
+}
+
+.sl-photo-pano {
+  cursor: grab;
+  touch-action: none;
+}
+
+.sl-photo-pano.sl-photo-dragging {
+  cursor: grabbing;
+}
+
+.sl-photo-flat[hidden],
+.sl-photo-pano[hidden] {
+  display: none;
+}
+
+.sl-photo-step {
+  position: absolute;
+  top: 50%;
+  z-index: 2;
+  width: 34px;
+  height: 44px;
+  margin-top: -22px;
+  border: 1px solid rgba(255, 255, 255, 0.18);
+  border-radius: 8px;
+  background: rgba(10, 10, 15, 0.62);
+  color: #fff;
+  font-size: 1.5rem;
+  line-height: 1;
+  cursor: pointer;
+}
+
+.sl-photo-step-prev {
+  left: 6px;
+}
+
+.sl-photo-step-next {
+  right: 6px;
+}
+
+.sl-photo-step:hover:not(:disabled),
+.sl-photo-step:focus-visible {
+  background: var(--sl-photo-fill);
+  outline: none;
+}
+
+.sl-photo-step:disabled {
+  opacity: 0.3;
+  cursor: default;
+}
+
+/* Nothing to step through until a photo shows. */
+.sl-photo-viewer:not([data-kind='flat']):not([data-kind='pano'])
+  .sl-photo-step {
+  display: none;
+}
+
 /* ── Short viewports ─────────────────────────────────────────────────────── */
 @media (max-height: 640px) {
   .street-level-panel-inner {