Fix category filter not hiding polygon/line notes, only points

TODO.adoc had this flagged: toggling a category off in the legend only
re-sliced the points source (_applyCategoryFilter), so a polygon or
line note (Measure's "Save as note") sharing that category stayed
visible. Added _linesByPath alongside the existing _pointsByPath,
tracked/cleaned up the same way, and reused for both the legend's
category scan and the filter's re-slice.

public/js/gpx.js

@@ -43,6 +43,7 @@ export class GpxPanelControl {
     this._visible = new Set(); // file paths currently shown on the map
     this._interactiveLayers = new Set(); // point layer ids with click/hover wired up
     this._pointsByPath = new Map(); // path -> its waypoints FeatureCollection, for the category legend
+    this._linesByPath = new Map(); // path -> its lines/polygons FeatureCollection, same reason (a polygon/line note also carries a category)
     this._hiddenCategories = new Set(); // category names toggled off in the legend
     this._openDownloadMenu = null; // the one gpx-tree__download-menu currently open, if any
 
@@ -597,6 +598,7 @@ export class GpxPanelControl {
     this._addClusterLayers(pointsId, path);
 
     if (points.features.length > 0) this._pointsByPath.set(path, points);
+    if (lines.features.length > 0) this._linesByPath.set(path, lines);
     this._updateLegend();
     this._applyCategoryFilter();
 
@@ -843,6 +845,7 @@ export class GpxPanelControl {
     if (this._map.getSource(pointsId)) this._map.removeSource(pointsId);
 
     this._pointsByPath.delete(path);
+    this._linesByPath.delete(path);
     this._updateLegend();
   }
 
@@ -853,8 +856,8 @@ export class GpxPanelControl {
   // on the map, not just a read-only color key.
   _updateLegend() {
     const categories = new Map(); // category name -> { color, icon }
-    for (const points of this._pointsByPath.values()) {
+    for (const collection of [...this._pointsByPath.values(), ...this._linesByPath.values()]) {
-      for (const feature of points.features) {
+      for (const feature of collection.features) {
         const category = feature.properties.category;
         if (category && !categories.has(category)) {
           categories.set(category, { color: feature.properties.color || TRACK_COLOR, icon: feature.properties.icon });
@@ -909,6 +912,16 @@ export class GpxPanelControl {
       const visible = points.features.filter((f) => !this._hiddenCategories.has(f.properties.category));
       source.setData({ type: "FeatureCollection", features: visible });
     }
+    // Same re-slicing for polygon/line notes sharing the "lines" source with
+    // plain tracks/routes — those have no `category` of their own, so
+    // `_hiddenCategories.has(undefined)` is always false and they're never
+    // affected by this, only a hidden Note (or other categorized) shape is.
+    for (const [path, lines] of this._linesByPath) {
+      const source = this._map.getSource(linesSourceId(path));
+      if (!source) continue;
+      const visible = lines.features.filter((f) => !this._hiddenCategories.has(f.properties.category));
+      source.setData({ type: "FeatureCollection", features: visible });
+    }
   }
 
   async _uploadFiles(fileList, folder) {