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_gpx_store.rb

@@ -0,0 +1,70 @@
+require_relative "test_helper"
+require "maptool/gpx_store"
+require "stringio"
+
+class GpxStoreTest < Minitest::Test
+  def setup
+    @store = Maptool::GpxStore.new(Dir.mktmpdir)
+  end
+
+  def test_save_returns_the_relative_path_and_lists_it_in_the_tree
+    path = @store.save(folder: "", filename: "ride.gpx", io: StringIO.new("<gpx></gpx>"))
+
+    assert_equal "ride.gpx", path
+    assert_equal ["ride.gpx"], @store.tree["children"].map { |c| c["name"] }
+  end
+
+  def test_fit_extension_is_preserved_not_forced_to_gpx
+    path = @store.save(folder: "", filename: "activity.fit", io: StringIO.new("binary"))
+    assert_equal "activity.fit", path
+  end
+
+  def test_unrecognized_extension_gets_gpx_appended
+    path = @store.save(folder: "", filename: "notes.txt", io: StringIO.new("x"))
+    assert_equal "notes.txt.gpx", path
+  end
+
+  def test_colliding_filenames_are_disambiguated
+    @store.save(folder: "", filename: "ride.gpx", io: StringIO.new("a"))
+    path = @store.save(folder: "", filename: "ride.gpx", io: StringIO.new("b"))
+
+    assert_equal "ride-1.gpx", path
+  end
+
+  def test_save_creates_the_target_folder
+    @store.save(folder: "trips/2026", filename: "ride.gpx", io: StringIO.new("x"))
+
+    folder = @store.tree["children"].find { |c| c["name"] == "trips" }["children"].find { |c| c["name"] == "2026" }
+    assert_equal ["ride.gpx"], folder["children"].map { |c| c["name"] }
+  end
+
+  def test_path_traversal_is_rejected
+    assert_raises(Maptool::GpxStore::InvalidPath) { @store.resolve_file("../../etc/passwd") }
+    assert_raises(Maptool::GpxStore::InvalidPath) { @store.save(folder: "../escape", filename: "x.gpx", io: StringIO.new("x")) }
+  end
+
+  def test_delete_file
+    @store.save(folder: "", filename: "ride.gpx", io: StringIO.new("x"))
+    @store.delete_file("ride.gpx")
+
+    assert_empty @store.tree["children"]
+  end
+
+  def test_delete_missing_file_raises_enoent
+    assert_raises(Errno::ENOENT) { @store.delete_file("nope.gpx") }
+  end
+
+  def test_delete_folder_refuses_the_store_root
+    assert_raises(Maptool::GpxStore::InvalidPath) { @store.delete_folder("") }
+  end
+
+  def test_move_relocates_and_disambiguates
+    @store.save(folder: "", filename: "ride.gpx", io: StringIO.new("a"))
+    @store.save(folder: "archive", filename: "ride.gpx", io: StringIO.new("b"))
+
+    new_path = @store.move(from: "ride.gpx", to_folder: "archive")
+
+    assert_equal "archive/ride-1.gpx", new_path
+    assert_empty @store.tree["children"].reject { |c| c["name"] == "archive" }
+  end
+end