feat(auto-play): defensive counter-attacks + garrison until 5 warriors

- Build phase: attack adjacent enemies before fortifying (counter-attack)
- Only march when 5+ warriors accumulated (no more premature attacks)
- Warriors at city fortify for defense bonus AND fight back

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

src/game/engine/scenes/tests/auto_play.gd

@@ -208,7 +208,7 @@ func _play_turn() -> void:
 
 	var city_pos: Vector2i = player.cities[0].position if not player.cities.is_empty() else Vector2i.ZERO
 
-	if military_count >= 1 and _turn_count >= 30:
+	if military_count >= 5:
 		# ATTACK PHASE: lock onto one target and march until it's destroyed
 		if _locked_target == Vector2i(-1, -1):
 			_locked_target = _find_attack_target(player)
@@ -240,7 +240,7 @@ func _play_turn() -> void:
 					u.fortified_turns = 0
 					_move_toward(u, target, game_map)
 	else:
-		# BUILD PHASE: fortify warriors at city, only scout explores
+		# BUILD PHASE: fortify at city, attack any adjacent enemies
 		for u: Variant in units_snapshot:
 			if not u.is_alive() or u.movement_remaining <= 0:
 				continue
@@ -249,12 +249,15 @@ func _play_turn() -> void:
 			if u.type_id == "dwarf_scout" and _turn_count <= 15:
 				_explore(u, player, game_map)
 			else:
-				# Fortify at city for defense bonus
+				# First: attack adjacent enemies (defensive counter-attack)
+				_try_attack_adjacent(u, game_map)
+				if not u.is_alive() or u.movement_remaining <= 0:
+					continue
+				# Then: fortify at city
 				if u.position == city_pos:
 					u.is_fortified = true
 					u.movement_remaining = 0
 				else:
-					# Move back to city
 					_move_toward(u, city_pos, game_map)