Detect a LiveTrack session ending the moment Garmin confirms it, not 30min later

Watched the session from the last two commits actually get saved:
Garmin updated its `end` field from the future 24h placeholder to
within a second of the last point's own time, immediately — much
faster than the recency-of-last-point fallback alone would have
noticed (that only flips after ACTIVE_WITHIN with no new points, so a
just-saved session with a last point seconds old would still read as
active for up to 30 more minutes).

Now checks end-already-in-the-past first (authoritative and near
instant when Garmin has set it), falling back to point recency only
when end still shows the future placeholder — the case an abandoned,
never-saved session never updates.

test/test_livetrack_client.rb

@@ -71,6 +71,22 @@ class LiveTrackClientTest < Minitest::Test
     assert Maptool::LiveTrackClient.summarize(result)["active"]
   end
 
+  # Verified live the same day: Garmin updates a real session's `end` from
+  # the future placeholder to within a second of the last point's own
+  # time immediately once the activity is saved on the watch — so a fresh
+  # last point alone isn't enough, `end` already being in the past has to
+  # win even then.
+  def test_summarize_marks_inactive_once_end_is_in_the_past_even_with_a_fresh_point
+    payloads = @client.send(:parse_payloads, FAKE_PAGE)
+    points = @client.send(:clean, @client.send(:search, payloads) { |n| n["trackPoints"] if n["trackPoints"].is_a?(Array) })
+    points[-1] = points[-1].merge("dateTime" => Time.now.utc.iso8601)
+    session = @client.send(:clean, @client.send(:search, payloads) { |n| n if n["sessionName"] })
+                      .merge("end" => (Time.now.utc - 1).iso8601)
+    result = Maptool::LiveTrackClient::Result.new(points: points, session: session)
+
+    refute Maptool::LiveTrackClient.summarize(result)["active"]
+  end
+
   def test_finds_the_planned_course_alongside_the_actual_track
     payloads = @client.send(:parse_payloads, FAKE_PAGE)
     course = @client.send(:clean, @client.send(:search, payloads) { |n| n["courses"].first if n["courses"].is_a?(Array) && !n["courses"].empty? })