Add a persisted test suite

`bundle exec rake test` (minitest, a default gem but pinned in
Gemfile for reproducibility) now covers what ad-hoc scripts kept
re-verifying by hand during development: Gpx/Fit/TrackStats parsing,
GpxStore/LiveTrackStore file/TTL logic, LiveTrackClient's payload
parsing, and app.rb's routes end to end via Rack::MockRequest.

MAPTOOL_DATA_DIR (new, app.rb) lets the suite point GPX_STORE/
LIVETRACK_STORE at a throwaway directory instead of real data/ —
without it every run would leave uploaded test files behind. Each
lib file's old `if __FILE__ == $0` self-check is now redundant with
real tests covering the same ground, so removed rather than kept as
a second copy of the same assertions. Wired into ci.yml so it isn't
just a local convenience.

test/test_livetrack_client.rb

@@ -0,0 +1,68 @@
+require_relative "test_helper"
+require "maptool/livetrack_client"
+
+# No real network calls here — Garmin's page format was verified manually
+# against real sessions during development; a synthetic fixture (matching
+# the real page's structure: several `self.__next_f.push(...)` calls, one
+# holding the track points nested under some data-fetching library's own
+# structure) is what actually needs to keep working over time.
+class LiveTrackClientTest < Minitest::Test
+  def setup
+    @client = Maptool::LiveTrackClient.new
+  end
+
+  FAKE_PAGE = <<~HTML.freeze
+    <html><body>
+    <script>self.__next_f.push([1,"6:[\\"$\\",\\"div\\",null,{}]"])</script>
+    <script>self.__next_f.push([1,"9:{\\"session\\":{\\"sessionName\\":\\"Test Ride\\",\\"start\\":\\"2026-01-01T00:00:00Z\\",\\"end\\":\\"2026-01-01T01:00:00Z\\"}}"])</script>
+    <script>self.__next_f.push([1,"10:{\\"unrelated\\":true,\\"nested\\":{\\"data\\":{\\"pages\\":[{\\"trackPoints\\":[{\\"position\\":{\\"lat\\":48.1,\\"lon\\":17.2},\\"dateTime\\":\\"2026-01-01T00:00:00Z\\",\\"totalDistanceMeters\\":\\"$undefined\\"},{\\"position\\":{\\"lat\\":48.2,\\"lon\\":17.3},\\"dateTime\\":\\"2026-01-01T00:01:00Z\\",\\"activityType\\":\\"CYCLING\\",\\"totalDistanceMeters\\":5000,\\"totalDurationSecs\\":600}]}]}}}"])</script>
+    </body></html>
+  HTML
+
+  def test_finds_track_points_and_session_across_separate_push_payloads
+    payloads = @client.send(:parse_payloads, FAKE_PAGE)
+
+    points = @client.send(:search, payloads) { |n| n["trackPoints"] if n["trackPoints"].is_a?(Array) }
+    assert_equal 2, points.size
+    assert_in_delta 48.1, points[0]["position"]["lat"]
+
+    session = @client.send(:search, payloads) { |n| n if n["sessionName"] }
+    assert_equal "Test Ride", session["sessionName"]
+  end
+
+  def test_undefined_sentinel_is_cleaned_to_nil
+    payloads = @client.send(:parse_payloads, FAKE_PAGE)
+    points = @client.send(:search, payloads) { |n| n["trackPoints"] if n["trackPoints"].is_a?(Array) }
+    cleaned = @client.send(:clean, points)
+
+    assert_nil cleaned[0]["totalDistanceMeters"]
+  end
+
+  def test_summarize_pulls_from_last_point_and_session
+    payloads = @client.send(:parse_payloads, FAKE_PAGE)
+    points = @client.send(:clean, @client.send(:search, payloads) { |n| n["trackPoints"] if n["trackPoints"].is_a?(Array) })
+    session = @client.send(:clean, @client.send(:search, payloads) { |n| n if n["sessionName"] })
+    result = Maptool::LiveTrackClient::Result.new(points: points, session: session)
+
+    summary = Maptool::LiveTrackClient.summarize(result)
+
+    assert_equal "Test Ride", summary["session_name"]
+    assert_equal "CYCLING", summary["activity_type"]
+    assert_equal 5000, summary["distance_meters"]
+    refute summary["active"], "session has an end timestamp"
+  end
+
+  def test_summarize_marks_active_when_session_has_no_end
+    payloads = @client.send(:parse_payloads, FAKE_PAGE)
+    points = @client.send(:clean, @client.send(:search, payloads) { |n| n["trackPoints"] if n["trackPoints"].is_a?(Array) })
+    session = @client.send(:clean, @client.send(:search, payloads) { |n| n if n["sessionName"] }).merge("end" => nil)
+    result = Maptool::LiveTrackClient::Result.new(points: points, session: session)
+
+    assert Maptool::LiveTrackClient.summarize(result)["active"]
+  end
+
+  def test_no_track_points_found_in_a_page_without_them
+    points = @client.send(:search, @client.send(:parse_payloads, "<html></html>")) { |n| n["trackPoints"] if n["trackPoints"].is_a?(Array) }
+    assert_nil points
+  end
+end