feat(mapillary): street-level layer core — coverage, sequences, viewer bridge, query engine

Camera-driven Mapillary coverage (z0–5 overview points from orbit, z11–14
ground-clamped sequence lines below 60 km), per-sequence image cones, an
embedded MapillaryJS viewer bridge with a camera-follow mode, sprite icons
for map features, and a query engine that turns a plan into a streamed
z14 tile fan-out. Registers an on-globe CC BY-SA 4.0 credit while enabled.

Co-Authored-By: Claude Fable 5.1 <[email protected]>

server/providers/mapillary/trim.js

@@ -0,0 +1,58 @@
+import { PbfReader, PbfWriter } from 'pbf';
+
+/** Field number of `layers` in a Mapbox Vector Tile, and of `name` in a layer. */
+const TILE_LAYER_FIELD = 3;
+const LAYER_NAME_FIELD = 1;
+
+/** Read a layer's name without touching its features. */
+function layerName(layerBytes) {
+  const pbf = new PbfReader(layerBytes);
+  let name = '';
+  pbf.readFields((tag, _result, reader) => {
+    if (tag !== LAYER_NAME_FIELD) return;
+    name = reader.readString();
+    reader.pos = reader.length; // the name is all we need
+  }, null);
+  return name;
+}
+
+/**
+ * Drop whole layers from a vector tile at the protobuf level. Nothing inside
+ * a kept layer is decoded or re-encoded, so a 12 MB tile whose bulk is an
+ * unused layer trims in a few milliseconds. Returns the input when nothing
+ * was dropped.
+ * @param {Buffer|Uint8Array} bytes
+ * @param {Iterable<string>} dropNames
+ */
+export function stripTileLayers(bytes, dropNames) {
+  const drop = new Set(dropNames || []);
+  if (!bytes?.length || !drop.size) return bytes;
+  const reader = new PbfReader(bytes);
+  const writer = new PbfWriter();
+  let dropped = false;
+  reader.readFields((tag, _result, pbf) => {
+    if (tag !== TILE_LAYER_FIELD) return; // pbf skips what we leave alone
+    const end = pbf.readVarint() + pbf.pos;
+    const layerBytes = bytes.subarray(pbf.pos, end);
+    pbf.pos = end;
+    if (drop.has(layerName(layerBytes))) {
+      dropped = true;
+      return;
+    }
+    writer.writeBytesField(TILE_LAYER_FIELD, layerBytes);
+  }, null);
+  return dropped ? Buffer.from(writer.finish()) : bytes;
+}
+
+/** Names of the layers inside a vector tile, in order. */
+export function listTileLayers(bytes) {
+  const names = [];
+  if (!bytes?.length) return names;
+  new PbfReader(bytes).readFields((tag, _result, pbf) => {
+    if (tag !== TILE_LAYER_FIELD) return;
+    const end = pbf.readVarint() + pbf.pos;
+    names.push(layerName(bytes.subarray(pbf.pos, end)));
+    pbf.pos = end;
+  }, null);
+  return names;
+}