Show session summary on hover over its LiveTrack marker

The track endpoint now merges the session summary into the marker's
GeoJSON properties (already computed for storage, just wasn't passed
through), and the marker gets the same hover-popup treatment GPX
points already have.

app.rb

@@ -258,7 +258,8 @@ module Maptool
       rescue LiveTrackClient::FetchError => e
         halt 502, json(error: "could not fetch track: #{e.message}")
       end
-      LIVETRACK_STORE.set_summary(session["id"], LiveTrackClient.summarize(result))
+      summary = LiveTrackClient.summarize(result)
+      LIVETRACK_STORE.set_summary(session["id"], summary)
 
       points = result.points
       coordinates = points.filter_map { |p| p.dig("position", "lon") && p.dig("position", "lat") && [p["position"]["lon"], p["position"]["lat"]] }
@@ -272,11 +273,14 @@ module Maptool
           {
             type: "Feature",
             geometry: { type: "Point", coordinates: coordinates.last },
-            properties: {
-              time: last["dateTime"],
-              speedMetersPerSec: last["speedMetersPerSec"],
-              heartRateBeatsPerMin: last["heartRateBeatsPerMin"],
-            },
+            # Merges the session summary in too — the point layer's hover
+            # popup (public/js/livetrack.js) reads it straight off here
+            # rather than needing a second fetch against /sessions.
+            properties: summary.merge(
+              "time" => last["dateTime"],
+              "speed_meters_per_sec" => last["speedMetersPerSec"],
+              "heart_rate_beats_per_min" => last["heartRateBeatsPerMin"]
+            ),
           },
         ]
       )