chore(client): add gdUnit4 test framework addon

Vendor gdUnit4 for Godot 4 client testing (D-030).

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

client/addons/gdUnit4/test/update/bbcodeView.tscn

@@ -0,0 +1,39 @@
+[gd_scene load_steps=3 format=3 uid="uid://c1rwx6anh3u3m"]
+
+[ext_resource type="Script" uid="uid://cw0cvkavw4c32" path="res://addons/gdUnit4/test/update/bbcodeView.gd" id="1"]
+[ext_resource type="Script" uid="uid://ogva4spkrtij" path="res://addons/gdUnit4/src/update/GdUnitUpdateClient.gd" id="6"]
+
+[node name="Control" type="Control"]
+layout_mode = 3
+anchors_preset = 15
+anchor_right = 1.0
+anchor_bottom = 1.0
+grow_horizontal = 2
+grow_vertical = 2
+script = ExtResource("1")
+
+[node name="HSplitContainer" type="HSplitContainer" parent="."]
+layout_mode = 1
+anchors_preset = 15
+anchor_right = 1.0
+anchor_bottom = 1.0
+grow_horizontal = 2
+grow_vertical = 2
+split_offset = 600
+
+[node name="TextEdit" type="TextEdit" parent="HSplitContainer"]
+layout_mode = 2
+
+[node name="RichTextLabel" type="RichTextLabel" parent="HSplitContainer"]
+use_parent_material = true
+layout_mode = 2
+tooltip_text = "test"
+bbcode_enabled = true
+
+[node name="GdUnitUpdateClient" type="Node" parent="."]
+script = ExtResource("6")
+
+[connection signal="text_changed" from="HSplitContainer/TextEdit" to="." method="_on_TextEdit_text_changed"]
+[connection signal="meta_clicked" from="HSplitContainer/RichTextLabel" to="." method="_on_RichTextLabel_meta_clicked"]
+[connection signal="meta_hover_ended" from="HSplitContainer/RichTextLabel" to="." method="_on_RichTextLabel_meta_hover_ended"]
+[connection signal="meta_hover_started" from="HSplitContainer/RichTextLabel" to="." method="_on_RichTextLabel_meta_hover_started"]