Add thank-you ending screen and a run timer

Defeating the bear (the run's final boss) now plays a dedicated
"Thank You For Playing" clip on the completion screen instead of the
generic bull-win video, with the run's finish time shown in place of
the usual "Bull Won!" title.

A run clock also starts when the player enters the arena (the run's
first fight), shown top-left on desktop only, and freezes the instant
the bear falls. Re-entering the arena after finishing a run restarts
the clock instead of leaving it stuck on the previous run's time.

Co-Authored-By: Claude Sonnet 5 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01MXBNaEBmrYDSMcv4NgUWtV

levels/run_state.gd

@@ -33,6 +33,14 @@ var cleared: Dictionary = {}
 ## loads — the player reads it on spawn — and is capped so it can't stack past BONUS_HP_CAP.
 var bonus_hp: int = 0
 const BONUS_HP_CAP: int = 2
+
+## Wall-clock run timer: starts the moment the player walks through the arena gate (the
+## run's first fight) and freezes the instant the bear falls, so the completion screen can
+## show a final time. Time.get_ticks_msec()-based — real time, not delta-summed — so it
+## keeps ticking correctly across the scene reload between the arena and the bear's den.
+var _timer_start_msec: int = -1
+var _timer_end_msec: int = -1
+var _timer_running: bool = false
 ## True once start_new_run() has built a run. Lets ensure_run() avoid wiping an active run
 ## when the shell reloads for each fight.
 var _run_active: bool = false
@@ -105,6 +113,9 @@ func start_new_run() -> void:
 	lobby_choice = null
 	cleared = {}
 	bonus_hp = 0
+	_timer_start_msec = -1
+	_timer_end_msec = -1
+	_timer_running = false
 	_run_active = true
 	run_started.emit()
 
@@ -154,3 +165,39 @@ func add_bonus_hp(amount: int) -> int:
 	var before := bonus_hp
 	bonus_hp = clampi(bonus_hp + amount, 0, BONUS_HP_CAP)
 	return bonus_hp - before
+
+
+## Begin the run clock. No-op while the clock is already running, so walking back through
+## the arena gate mid-run can't restart it — but once it's been stopped (the bear is dead
+## and the player has looped back to the arena to go again), the next call restarts it from
+## zero rather than staying stuck showing the previous run's final time.
+func start_run_timer() -> void:
+	if _timer_running:
+		return
+	_timer_start_msec = Time.get_ticks_msec()
+	_timer_end_msec = -1
+	_timer_running = true
+
+
+## Freeze the run clock — called the instant the bear falls, so the recorded time is the
+## kill moment itself, not whatever the win-screen's celebratory delay adds on top.
+func stop_run_timer() -> void:
+	if not _timer_running:
+		return
+	_timer_end_msec = Time.get_ticks_msec()
+	_timer_running = false
+
+
+## Seconds elapsed since the timer started (live while running, held steady once
+## stop_run_timer() has been called). 0 before the timer has ever started.
+func run_elapsed() -> float:
+	if _timer_start_msec < 0:
+		return 0.0
+	var end_msec := Time.get_ticks_msec() if _timer_running else _timer_end_msec
+	return float(end_msec - _timer_start_msec) / 1000.0
+
+
+## Whether the run clock has been started (the player has entered the arena at least once
+## this run). Lets the HUD hide the timer readout until there's a time worth showing.
+func run_timer_started() -> bool:
+	return _timer_start_msec >= 0

levels/to_the_arena_level.gd

@@ -8,5 +8,6 @@ func _ready() -> void:
 func _on_body_entered(body: Node3D) -> void:
 	if not body.is_in_group("player"):
 		return
+	Run.start_run_timer()
 	Run.choose_level(&"arena")
 	get_tree().change_scene_to_file(Run.active_level().scene_path)