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.

TODO.md

@@ -54,11 +54,14 @@ venues, and see enough authored variety that a second shift does not feel like a
 
 ### 0.8.1 First-shift tutorial
 
-- [ ] Write the tutorial beat sheet: menu → movement/look → focus and target cycling → action
+- [x] Write the tutorial beat sheet: menu → movement/look → focus and target cycling → action
       wheel → access inspection → polite direction → formal warning/body camera → radio →
-      shift review. Keep it to 6–8 beats and one safe, compliant NPC.
-- [ ] Add a tutorial state machine independent of the normal shift FSM. It must be skippable,
-      restartable and deterministic, and must not change the outcome of the live shift.
+      shift review. Eight beats and a safe compliant visitor are specified in
+      [`docs/tutorial.md`](docs/tutorial.md).
+- [x] Add a tutorial state machine independent of the normal shift FSM. `Tutorial` in
+      `src/game/tutorial.gd` owns the eight beats, accepts only the current beat's action,
+      supports skip/restart and has deterministic headless tests. GameManager/UI wiring starts
+      with the contextual-prompt task.
 - [ ] Add contextual prompts that advance on the performed action, not on a timer. Prompts must
       not block normal input or repeat after the player has learned the control.
 - [ ] Stage a safe encounter with one compliant visitor; no emergency, threat or crowd panic in