feat: use authored category names for mods

Store categories as authored strings. Trim and deduplicate without changing case, compare without case sensitivity, and keep all observed categories available to filters and editors.

scenes/components/mod_category_editor.tscn

@@ -0,0 +1,57 @@
+[gd_scene format=3]
+
+[ext_resource type="Script" path="src/View/ModCategoryEditor.cs" id="1"]
+
+[node name="ModCategoryEditor" type="Control"]
+custom_minimum_size = Vector2(440, 260)
+size_flags_horizontal = 3
+script = ExtResource("1")
+
+[node name="Layout" type="VBoxContainer" parent="."]
+layout_mode = 1
+anchors_preset = 15
+anchor_right = 1.0
+anchor_bottom = 1.0
+grow_horizontal = 2
+grow_vertical = 2
+theme_override_constants/separation = 4
+
+[node name="Caption" type="Label" parent="Layout"]
+layout_mode = 2
+text = "mod_categories/title"
+
+[node name="Base" type="GridContainer" parent="Layout"]
+layout_mode = 2
+columns = 4
+
+[node name="Custom" type="HFlowContainer" parent="Layout"]
+layout_mode = 2
+
+[node name="Input" type="HBoxContainer" parent="Layout"]
+layout_mode = 2
+
+[node name="Code" type="LineEdit" parent="Layout/Input"]
+layout_mode = 2
+size_flags_horizontal = 3
+placeholder_text = "mod_categories/code"
+
+[node name="Add" type="Button" parent="Layout/Input"]
+layout_mode = 2
+text = "mod_categories/add"
+
+[node name="Suggestions" type="OptionButton" parent="Layout"]
+layout_mode = 2
+fit_to_longest_item = false
+
+[node name="PrimaryRow" type="HBoxContainer" parent="Layout"]
+layout_mode = 2
+
+[node name="Caption" type="Label" parent="Layout/PrimaryRow"]
+layout_mode = 2
+text = "mod_categories/primary"
+
+[node name="Primary" type="OptionButton" parent="Layout/PrimaryRow"]
+layout_mode = 2
+fit_to_longest_item = false
+text_overrun_behavior = 3
+size_flags_horizontal = 3