feat(progression): composition root and event republisher (slice 9)

ProgressionRoot autoload builds the JSON stores from
GlobalizePath("user://"), loads the Profile, reads the authored upgrade
tables into a SkillCatalogue, and owns the ProgressionService. Every
mutating operation is wrapped so draining and republishing cannot be
forgotten - the one risk of the DrainEvents design, now confined to one
file.

ProgressionEventRepublisher turns domain records into EventBus signals
(ADR-0004), so existing subscribers and scene wiring keep working. New
RunEnded signal: GameOverScreen reads Lives directly today, which is the
last-life soft-lock.

Registered after SkillManager, since the skill catalogue is built from
AvailableSkills. GameStateStore stays until slice 10 moves the callers.

Transitional: LevelStarted is republished with a catalogue index because
GhostManager names files ghost_level_{index}.json.

project.godot

@@ -54,6 +54,7 @@ StatisticsEventHandler="*res://scripts/Events/StatisticsEventHandler.cs"
 CoinStateHandler="*res://scripts/Events/CoinStateHandler.cs"
 LivesStateHandler="*res://scripts/Events/LivesStateHandler.cs"
 SkillCollectHandler="*res://scripts/Events/SkillCollectHandler.cs"
+ProgressionRoot="*res://objects/progression_root.tscn"
 GameStateStore="*res://Autoloads/GameStateStore.cs"
 GameManager="*res://objects/game_manager.tscn"