fix(street-level): KartaView marker and camera direction; remaining review P4s

Marker and direction (reported on the PR):
- KartaView has its own marker, a purple view cone (Street View's is
  blue), not GEV's default pin that Mapillary uses.
- The camera direction (marker, cones, FOLLOW, a panorama's centre) is
  the direction of travel to the next photo a few metres on. KartaView's
  heading is the device compass: whole drives read 0 (no compass) and
  others sit a steady ~110° off. Until the drive loads the compass stands
  in (0 = unknown), and the pose is sent again once the course is known.

Remaining P4s from the review of #1121:
- Segment chaining is linear (a per-point cursor) and capped at 20,000
  segments a tile and 5,000 points a line: a hostile tile of 60k segments
  sharing one point took 1.5 s, now tens of ms.
- Decoded tiles are dropped when KartaView is switched off.
- No network / a refused request says so and is not retried as a timeout;
  an unreadable answer says so.
- A docked flat photo skips the 2,560 px download until the viewer grows.
- The panel counts the drive's photos (countActivePhotos), not the thinned
  page of cones (2,250, not 217).
- After a GPU reset the viewer redraws the photo itself, so a lookup the
  user started is not cancelled; a failure is still reported.
- The gate's keyless page lights KartaView and checks it draws with no key;
  the fixture answers the sequence count; the line-click step checks the
  camera looks along the drive when the compass says 200°.
- README/CHANGELOG show the share-link form the app writes.

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

scripts/qa-street-level.mjs

@@ -464,6 +464,45 @@ async function assertKeylessGate(page) {
   assert.match(chip.title, /MAPILLARY_CLIENT_TOKEN/);
 }
 
+/**
+ * With no Mapillary key the panel points at KartaView, which needs none:
+ * lit, it draws coverage and the layer is not key-gated.
+ */
+async function assertKeylessKartaView(page) {
+  assert.match(
+    await page.$eval('#sl-coverage-meta', (node) => node.textContent),
+    /light KARTAVIEW/,
+    'KEY REQUIRED points at KartaView',
+  );
+  for (let attempt = 0; attempt < 4; attempt++) {
+    await page.evaluate((at) => {
+      const v = window.__godsEyeView.viewer;
+      v.camera.cancelFlight?.();
+      const C = v.camera.positionCartographic.constructor;
+      v.camera.setView({
+        destination: v.scene.globe.ellipsoid.cartographicToCartesian(
+          C.fromDegrees(at.lon, at.lat, at.height),
+        ),
+        orientation: { heading: 0, pitch: at.pitch, roll: 0 },
+      });
+    }, PARK);
+    await sleep(1000);
+  }
+  await clickPanelControl(
+    page,
+    '#sl-provider-chips [data-chip-id="kartaview"]',
+  );
+  await waitForCoverage(page);
+  const state = await page.evaluate(() => ({
+    status: document.getElementById('sl-status').textContent,
+    keyRequired: window.__godsEyeView.dataManager.layers
+      .get('street-level')
+      .module.getUIState().keyRequired,
+  }));
+  assert.equal(state.keyRequired, false);
+  assert.doesNotMatch(state.status, /KEY/);
+}
+
 /**
  * Runs in the page. Find a point where a real click picks `prefix` + `id` (any
  * id when null), searched around `points` ([lon, lat]), the aimed billboards,
@@ -942,6 +981,15 @@ async function main() {
               ),
               `cones for the whole drive: ${JSON.stringify((await ui()).sequence)}`,
             );
+            // The drive runs north; the photos' compass says 200°.
+            assert.ok(
+              await uiUntil(
+                (u) =>
+                  Number.isFinite(u.street.bearing) &&
+                  Math.min(u.street.bearing, 360 - u.street.bearing) < 2,
+              ),
+              `the camera looks along the drive, not where the compass points: ${(await ui()).street.bearing}`,
+            );
           }
           const before = street.imageId;
           await clickPanelControl(page, '.sl-kv-step-next');
@@ -2444,7 +2492,7 @@ async function main() {
       );
       if (fixtures)
         await step(
-          'keyless install (a second page, no key on the server) gates the controls and reports KEY REQUIRED',
+          'keyless install (a second page, no key on the server) gates the controls and reports KEY REQUIRED, and KartaView draws there',
           async () => {
             const keyless = await browser.newPage();
             await keyless.setViewport(VIEWPORTS[0]);
@@ -2453,6 +2501,7 @@ async function main() {
             await boot(keyless, url);
             await expandStrip(keyless);
             await assertKeylessGate(keyless);
+            await assertKeylessKartaView(keyless);
             renderErrorsSeen.push(
               ...(await readRenderErrors(keyless)).map(
                 (text) => `[keyless] scene.renderError: ${text}`,