chore(tooling): install GUT v9.6.0 test framework

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

addons/gut/thing_counter.gd

@@ -0,0 +1,55 @@
+var things = {}
+
+func get_unique_count():
+	return things.size()
+
+
+func add_thing_to_count(thing):
+	if(!things.has(thing)):
+		things[thing] = 0
+
+
+func add(thing):
+	if(things.has(thing)):
+		things[thing] += 1
+	else:
+		things[thing] = 1
+
+
+func has(thing):
+	return things.has(thing)
+
+
+func count(thing):
+	var to_return = 0
+	if(things.has(thing)):
+		to_return = things[thing]
+	return to_return
+
+
+func sum():
+	var to_return = 0
+	for key in things:
+		to_return += things[key]
+	return to_return
+
+
+func to_s():
+	var to_return = ""
+	for key in things:
+		to_return += str(key, ":  ", things[key], "\n")
+	to_return += str("sum: ", sum())
+	return to_return
+
+
+func get_max_count():
+	var max_val = null
+	for key in things:
+		if(max_val == null or things[key] > max_val):
+			max_val = things[key]
+	return max_val
+
+
+func add_array_items(array):
+	for i in range(array.size()):
+		add(array[i])