fix(street-level): address gekh's review of #768

P0
- tileMath: lonToTileX(180) wrapped to column 0, so a whole-world view at
  z1 loaded only the western column; 180 is now the last column.
- coverage.loadTile: a superseded request (after a retire or clear) still
  deleted the newer request's pending entry and loading count in `finally`,
  letting a duplicate load attach lines that nothing could remove. Only the
  request that still owns the key attaches its tile or settles the key.

P1
- view/tileMath: a view across the date line read as a ~358 deg box and
  loaded tiles on the far side of the globe. visibleBbox now returns
  west > east for such views and tilesForBbox splits them at +/-180;
  viewCentre averages across the line.
- decode: the parts of a multi-line sequence were joined into one line,
  drawing straight segments over capture gaps. Each part is now its own
  line (`parts`); later parts carry `~n` in their pick id, and picking or
  recolouring any part acts on the whole sequence.
- viewerHost: a prewarmed MapillaryJS viewer was never destroyed, leaking
  its WebGL context. Prewarmed adapters are tracked and released on
  unmount, at once when the layer went off mid-load, and per provider when
  only that provider is switched off.
- nearestImage took the first record the API returned; it now takes the
  closest one that passes the filter.

P2
- groundCast: the cache was cleared after a request counted its corners,
  dropping ones it relied on; it is now cleared first.
- streetLevelControls: the viewer was resized on every render (every frame
  while a panorama is dragged); the ResizeObserver handles size changes and
  the viewer is resized once when it opens. The legend now rebuilds when its
  entries change, not only their count.
- panelPositionControls: the portable-panel paths this PR added called the
  CCTV viewport sync directly; they go through onPanelResized, which the
  shell routes to CCTV. The "Compose camera panel controls" JSDoc is back on
  _initCctvPanel.

New tests: zoom-1 columns, date-line tiles and bbox, multi-part decode and
part pick ids, nearest image, prewarmed viewer release, and the cache
ordering (fails on the old order).

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

src/layers/streetLevel/viewerHost.js

@@ -9,6 +9,12 @@ export function createViewerHost({ state, parts }) {
   /** @type {{id: string, promise: Promise<object>}|null} */
   let mounting = null;
   let openSeq = 0;
+  /**
+   * Adapters stood up by `prewarm` that are not the active one: each holds a
+   * live viewer (a WebGL context for MapillaryJS) until `unmount` releases it.
+   * @type {Map<string, object>}
+   */
+  const warmed = new Map();
 
   function notify() {
     state.notify?.();
@@ -84,6 +90,7 @@ export function createViewerHost({ state, parts }) {
         throw new Error('Street-level viewer was closed');
       }
       active = { id: entry.def.id, adapter, unsubscribe };
+      warmed.delete(entry.def.id);
       adapter.setRenderMode?.(state.street.renderMode);
       return adapter;
     })();
@@ -193,22 +200,44 @@ export function createViewerHost({ state, parts }) {
     const host = state.street.host;
     if (!host || !state.enabled) return;
     for (const entry of entries) {
+      const adapter = entry.instance.viewer;
+      if (!adapter.prewarm || !entry.on) continue;
       try {
-        await entry.instance.viewer.prewarm?.(host);
+        await adapter.prewarm(host);
       } catch {
         /* the real open reports errors */
       }
+      if (active?.id === entry.def.id) continue;
+      // Switched off while it loaded: release it now rather than keep it.
+      if (!state.enabled || !entry.on) adapter.unmount();
+      else warmed.set(entry.def.id, adapter);
     }
   }
 
-  /** Tear the mounted adapter down (layer disabled or destroyed). */
-  function unmount() {
-    close();
-    mounting = null;
-    if (!active) return;
-    active.unsubscribe();
-    active.adapter.unmount();
-    active = null;
+  /**
+   * Tear viewers down: every one (layer disabled or destroyed), or only the
+   * given provider's, active or prewarmed (that provider switched off).
+   * @param {string} [providerId]
+   */
+  function unmount(providerId) {
+    if (
+      !providerId ||
+      active?.id === providerId ||
+      mounting?.id === providerId
+    ) {
+      close();
+      mounting = null;
+      if (active) {
+        active.unsubscribe();
+        active.adapter.unmount();
+        active = null;
+      }
+    }
+    for (const [id, adapter] of warmed) {
+      if (providerId && id !== providerId) continue;
+      warmed.delete(id);
+      adapter.unmount();
+    }
   }
 
   return {