fix(street-level): KartaView QA round — archived photos, connection budget, paging, ‹ ›

From two agentic QA passes (UX and failure modes):
- A line click opens the nearest photo that can be shown: archived photos
  (409; a HEAD says 200) and records without files are skipped, a few at
  most, else 'KartaView's photos here are archived'. ‹ › skip them too.
- api.kartaview.org is HTTP/1.1 (six connections): tiles take three,
  lookups two, sequence pages one, so a lookup never times out behind
  tiles; a timed-out lookup is asked once more; waits are capped at 10 s.
- Sequence pages follow photo ids, not the index: a photo's page is found
  by search, a neighbour page joins near an edge, so ‹ › neither skip at
  page edges nor loop past gaps. Pages are 500 photos (~1.2 MB).
- ‹ › open through the core without framing: loading, errors and cones
  behave as for any open; presses step on from the photo on its way; the
  ends disable up front.
- Cones ignore the hidden IMAGERY / SINCE filters; no 'Selected' swatch
  for a source whose lines never highlight; 'no KartaView photos in view';
  an unreadable tile is not cached as empty; a 0,0 fix is no photo; a
  failed lookup's error goes when another source is lit; the link goes
  through the image proxy; a stalled panorama shows its front view after
  15 s instead of 60.

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

src/layers/streetLevel/uiState.js

@@ -18,6 +18,7 @@ import { COLORS } from './policy.js';
  * @property {boolean} [groundClick]
  * @property {Array<'pano'|'since'>} [filters]
  * @property {{noun: string, action: string}|null} [coverageLabel]
+ * @property {boolean} [highlightsSequence]   Its lines turn cyan when their sequence is selected.
  */
 
 /**
@@ -95,7 +96,13 @@ export function composeUIState({
       label: provider.name,
       color: provider.color,
     }));
-  if (legend.length)
+  // "Selected" only beside a source whose lines turn cyan when selected.
+  if (
+    active.some(
+      (provider) =>
+        provider.groundClick !== true && provider.highlightsSequence !== false,
+    )
+  )
     legend.push({ key: 'selected', label: 'Selected', color: COLORS.selected });
   return {
     enabled,