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.test.mjs

@@ -236,3 +236,25 @@ test('a key-gated layer offers the switched-off sources that would draw with a k
     [],
   );
 });
+
+test('a source whose lines never show a selection lists no Selected swatch, and names its own lines', () => {
+  const kartaView = provider({
+    id: 'kartaview',
+    name: 'KartaView',
+    color: '#635bff',
+    highlightsSequence: false,
+    coverageLabel: {
+      noun: 'streets',
+      action: 'click a line for its nearest photo',
+    },
+  });
+  const ui = composeUIState({ ...base, providers: [kartaView] });
+  assert.deepEqual(
+    ui.legend.map((entry) => entry.key),
+    ['kartaview'],
+  );
+  assert.deepEqual(ui.coverage.label, {
+    noun: 'streets',
+    action: 'click a line for its nearest photo',
+  });
+});