Add the first-shift tutorial design and state machine

Write the eight-beat tutorial sheet, its safe visitor script, persistence and
replay rules. Add a deterministic, skippable/restartable Tutorial RefCounted
state machine with headless tests. UI/GameManager wiring remains the next task.
Headless 235/235, Python 94/94.

src/test/tests/test_tutorial.gd

@@ -0,0 +1,49 @@
+extends RefCounted
+## Deterministic headless tests for the first-shift tutorial state machine.
+
+const Tutorial := preload("res://src/game/tutorial.gd")
+
+func test_tutorial_advances_only_on_the_expected_action() -> bool:
+	var tutorial := Tutorial.new()
+	tutorial.start()
+	var a := TestUtils.check(tutorial.current()["id"] == "arrive", "starts at arrival")
+	var b := TestUtils.check(not tutorial.advance("wheel_opened"), "wrong action is ignored")
+	var c := TestUtils.check(tutorial.advance("moved"), "movement advances")
+	var d := TestUtils.check(tutorial.current()["id"] == "focus", "moves to focus")
+	var e := TestUtils.check(tutorial.advance("cycled"), "target cycling advances")
+	var f := TestUtils.check(tutorial.current()["id"] == "wheel", "moves to the action wheel")
+	return a and b and c and d and e and f
+
+func test_tutorial_runs_all_beats_and_completes() -> bool:
+	var tutorial := Tutorial.new()
+	tutorial.start()
+	var events := ["moved", "cycled", "wheel_opened", "inspected",
+		"polite_direction", "formal_warning", "radio_submitted", "review_opened"]
+	var ok := true
+	for event in events:
+		ok = ok and tutorial.advance(event)
+	ok = ok and tutorial.is_complete()
+	ok = ok and not tutorial.is_skipped()
+	ok = ok and tutorial.progress() == Vector2i(Tutorial.BEATS.size(), Tutorial.BEATS.size())
+	return TestUtils.check(ok, "all eight beats complete in order")
+
+func test_tutorial_accepts_body_camera_for_warning() -> bool:
+	var tutorial := Tutorial.new()
+	tutorial.start()
+	for event in ["moved", "cycled", "wheel_opened", "inspected", "polite_direction"]:
+		tutorial.advance(event)
+	var a := TestUtils.check(tutorial.advance("body_camera"), "body camera satisfies warning")
+	var b := TestUtils.check(tutorial.current()["id"] == "radio", "advances to radio")
+	return a and b
+
+func test_tutorial_skip_and_restart() -> bool:
+	var tutorial := Tutorial.new()
+	tutorial.start()
+	var a := TestUtils.check(tutorial.advance("moved"), "one beat completed")
+	tutorial.skip()
+	var b := TestUtils.check(tutorial.is_complete() and tutorial.is_skipped(), "skip completes tutorial")
+	var c := TestUtils.check(not tutorial.advance("moved"), "completed tutorial is inert")
+	tutorial.restart()
+	var d := TestUtils.check(not tutorial.is_complete() and not tutorial.is_skipped(), "restart clears flags")
+	var e := TestUtils.check(tutorial.current()["id"] == "arrive", "restart returns to beat one")
+	return a and b and c and d and e