Add visual harmonization tests for editor UI components and ground finish chooser

- Implemented `test_editor_visual_harmonization.gd` to validate the Stickman editor and prop editor UI layouts, ensuring proper functionality and visual consistency.
- Created `test_editor_visual_theme.gd` to verify the loading and application of visual themes in the editor, including semantic overrides and default values.
- Introduced `test_phase19_ground_finish_chooser.gd` to test the ground finish chooser's functionality, including layout responsiveness, selection behavior, and interaction with the stage.
- Added new scripts for ground finish preview and chooser UI components to enhance the editor's visual representation of ground finishes.

scripts/stage/sandbox_theme.gd

@@ -125,6 +125,36 @@ func _apply_phase19_defaults() -> void:
 		if not asset_selector.has(key):
 			asset_selector[key] = starter_defaults[key]
 	popups["asset_selector"] = asset_selector
+	var ground_finish_defaults: Dictionary = {
+		"card_width": 880,
+		"max_height_ratio": 0.86,
+		"screen_margin": 24,
+		"choice_height": 96,
+		"choice_preview_height": 48,
+		"choice_font_size": 18,
+		"choice_min_width": 104,
+		"choice_corner_radius": 12,
+		"compact_choice_height": 50,
+		"compact_choice_preview_height": 22,
+		"compact_choice_font_size": 16,
+		"compact_grid_gap": 6,
+		"compact_layout_max_width": 600,
+		"compact_layout_max_height": 460,
+		"compact_height_ratio": 0.89,
+		"preview_height": 128,
+		"compact_preview_height": 88,
+		"preview_min_width": 224,
+		"preview_corner_radius": 12,
+		"preview_surface": "#151C28",
+		"preview_border": "#39465B",
+		"grid_gap": 8,
+		"wide_layout_min_width": 760,
+	}
+	var ground_finish: Dictionary = popups.get("ground_finish_chooser", {}).duplicate(true)
+	for key: String in ground_finish_defaults:
+		if not ground_finish.has(key):
+			ground_finish[key] = ground_finish_defaults[key]
+	popups["ground_finish_chooser"] = ground_finish
 	_config["popups"] = popups
 	var overlays: Dictionary = _config.get("overlays", {}).duplicate(true)
 	var gizmos: Dictionary = overlays.get("gizmos", {}).duplicate(true)