Complete the DamageEvent migration: one deal() entry point for every attacker

The bull's Hitbox already routed through DamageEvent, but the spear, the bear's
maul, and the matador's reach-gore still did raw Object.call(&"take_sword_hit", ...)
— the exact scattered string paths DamageEvent was meant to retire. Add a single
static DamageEvent.deal(target, cause, at, source, knock_up) that builds the typed
event and hands it to receive_damage(), falling back to the legacy string call for
any not-yet-migrated victim, and route all four attackers (Hitbox included) through
it. The damage_pipeline characterization test proves the bull's outcomes are
unchanged.

Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01Pq1VX2o1ZfiNRdCjD294wf

hitbox.gd

@@ -80,17 +80,8 @@ func _apply_hit(body: Node3D) -> void:
 		return
 	_hit_this_swing[body] = true
 	_did_hit = true
-	if body.has_method(&"receive_damage"):
-		var event := DamageEvent.make(DamageEvent.cause_from(damage_cause), body.global_position, self)
-		if knock_up > 0.0:
-			event.knock_up = _knock_up_for(body)
-		body.call(&"receive_damage", event)
-	else:
-		body.call(&"take_sword_hit", damage_cause)
-		if knock_up > 0.0:
-			var v := _knock_up_for(body)
-			if v > 0.0:
-				body.call(&"apply_knock_up", v)
+	var ku := _knock_up_for(body) if knock_up > 0.0 else 0.0
+	DamageEvent.deal(body, DamageEvent.cause_from(damage_cause), body.global_position, self, ku)
 
 
 # Scale the pop by how far the body is from this hitbox's origin (planar). See the export docs.