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

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

addons/gut/double_templates/double_data_template.txt

@@ -0,0 +1,22 @@
+var __gutdbl_values = {
+	thepath = '{path}',
+	subpath = '{subpath}',
+	stubber = {stubber_id},
+	spy = {spy_id},
+	gut = {gut_id},
+	singleton_name = '{singleton_name}',
+	singleton = {singleton_id},
+	is_partial = {is_partial},
+	doubled_methods = {doubled_methods},
+}
+var __gutdbl = load('res://addons/gut/double_tools.gd').new(self)
+
+# Here so other things can check for a method to know if this is a double.
+func __gutdbl_check_method__():
+	pass
+
+# Cleanup called by GUT after tests have finished.  Important for RefCounted
+# objects.  Nodes are freed, and won't have this method called on them.
+func __gutdbl_done():
+	__gutdbl = null
+	__gutdbl_values.clear()

addons/gut/double_templates/function_template.txt

@@ -0,0 +1,9 @@
+{func_decleration}
+	if(__gutdbl == null):
+		return
+
+	__gutdbl.spy_on('{method_name}', {param_array})
+	if(__gutdbl.is_stubbed_to_call_super('{method_name}', {param_array})):
+		{super_call}
+	else:
+		return await __gutdbl.handle_other_stubs('{method_name}', {param_array})

addons/gut/double_templates/init_template.txt

@@ -0,0 +1,4 @@
+{func_decleration}:
+	super({super_params})
+	__gutdbl.spy_on('{method_name}', {param_array})
+

addons/gut/double_templates/script_template.txt

@@ -0,0 +1,13 @@
+# ##############################################################################
+# Gut Doubled Script
+# ##############################################################################
+{extends}
+
+# ------------------------------------------------------------------------------
+# GUT stuff
+# ------------------------------------------------------------------------------
+{double_data}
+
+# ------------------------------------------------------------------------------
+# Doubled Methods
+# ------------------------------------------------------------------------------

addons/gut/double_templates/singleton_template.txt

@@ -0,0 +1,16 @@
+{extends}
+
+{constants}
+
+{signals}
+
+{properties}
+
+# ------------------------------------------------------------------------------
+# GUT stuff
+# ------------------------------------------------------------------------------
+{double_data}
+
+# ------------------------------------------------------------------------------
+# Doubled Methods
+# ------------------------------------------------------------------------------