fix(street-level): Panoramax IC8 review — line geometry budget, caches, attribution, tests

From a five-lens IC8 review (correctness, security, tests with mutation
testing, performance, UX):
- P0: over Paris at 12–60 km the unsimplified z10–z12 lines sent ~2M
  points to Cesium's ground-polyline builder (gigabytes of geometry; the
  tab hung). decode.js now simplifies lines (Douglas–Peucker, 4 tile
  units: 6–10% of the points), and lineCoverage gains an opt-in point
  budget (`maxPoints`, 10,000 a tile for Panoramax).
- Decoded coverage tiles are kept (KartaView's tile cache moves to the
  shared tileCache.js); a sequence's z15 picture lists are kept and load
  on their own connection; cones know their tiles from the start of a
  load, so a picture opening meanwhile re-centres them and ‹ › no longer
  restarts the load.
- The HD panorama loads only for the expanded viewer (a docked one on a
  dense screen asked for 3 MB originals) and is aborted when another
  photo opens; picture files over 48 MB or 16,384 px are refused; a
  bitmap no renderer took after a context loss is closed.
- A nearest lookup survives one of its two searches failing; only a
  timeout is retried; offline reads as unreachable; Retry-After is
  capped at five minutes; the search box stays on the map at ±180°;
  cones near both edges of a narrow (high-latitude) tile read both.
- Every producer is credited (app and photographer); with none to name,
  the caption says "via <instance>" rather than crediting the host.
- Esc anywhere in the docked viewer (toolbar, caption) clears the
  sequence before the panel takes it. A filter that hides every density
  dot says so; wording aligned ("coverage", "photo").
- Tests for every surviving mutant (Esc consumed, keepOrder and dot-size
  wiring, licence in the core, limiter aborts, radius floor, bbox corner,
  first-producer-only, byte and size caps), a limiter test, and a gate
  fixture that answers box searches and leaves out pictures facing away;
  the gate now clicks over the other sequence's pictures, so only the
  line click's own-sequence lookup can pass.

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

scripts/fixtures/street-level/panoramax.mjs

@@ -112,7 +112,11 @@ function item(picture, pictures) {
       sd: { href: `${files}/sd.jpg` },
       thumb: { href: `${files}/thumb.jpg` },
     },
-    links: [...link('prev', sibling(-1)), ...link('next', sibling(1))],
+    links: [
+      ...link('prev', sibling(-1)),
+      ...link('next', sibling(1)),
+      { rel: 'via', href: HOST },
+    ],
   };
 }
 
@@ -231,11 +235,9 @@ export function answerPanoramaxRequest({ method, url }) {
         .map((p) => item(p, pictures)),
     });
   }
-  const [lon, lat] = (q.get('place_position') || '').split(',').map(Number);
-  const radius = Number((q.get('place_distance') || '0-50').split('-')[1]);
   const filter = q.get('filter') || '';
   const since = q.get('datetime')?.split('/')[0];
-  const near = pictures
+  const kept = pictures
     .filter(
       (p) => !q.get('collections') || p.sequenceId === q.get('collections'),
     )
@@ -246,7 +248,29 @@ export function answerPanoramaxRequest({ method, url }) {
           ? !p.isPano
           : true,
     )
-    .filter((p) => !since || Date.parse(p.datetime) >= Date.parse(since))
+    .filter((p) => !since || Date.parse(p.datetime) >= Date.parse(since));
+  // A box: every picture in it, in no particular order (id order here).
+  if (q.has('bbox')) {
+    const [west, south, east, north] = q.get('bbox').split(',').map(Number);
+    return json({
+      type: 'FeatureCollection',
+      features: kept
+        .filter(
+          (p) =>
+            p.lon >= west && p.lon <= east && p.lat >= south && p.lat <= north,
+        )
+        .sort((a, b) => a.id.localeCompare(b.id))
+        .slice(0, Number(q.get('limit')) || 10)
+        .map((p) => item(p, pictures)),
+    });
+  }
+  const [lon, lat] = (q.get('place_position') || '').split(',').map(Number);
+  const radius = Number((q.get('place_distance') || '0-50').split('-')[1]);
+  // As the API does, even at the widest tolerance: a place behind a
+  // picture (every one looks east) is not in it.
+  const facing = (p) => lon >= p.lon - 1e-7;
+  const near = kept
+    .filter(facing)
     .map((p) => ({ p, metres: metresApart({ lon, lat }, p) }))
     .filter(({ metres }) => metres <= radius)
     .sort((a, b) => a.metres - b.metres)