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.

editor_visual_theme.json

@@ -0,0 +1,43 @@
+{
+  "version": "1.0",
+  "chrome": {
+    "colors": {
+      "background": "#171B24F2",
+      "surface": "#252B38FA",
+      "surface_hover": "#30394A",
+      "text": "#F5F7FA",
+      "text_muted": "#AAB2C0",
+      "edit": "#22C6FF",
+      "preview": "#22C6FF66",
+      "focus": "#8BD9FF",
+      "action_primary": "#087DBA",
+      "destructive": "#E66B75",
+      "border": "#FFFFFF33",
+      "disabled": "#77808F",
+      "saved": "#8FD6A4",
+      "dirty": "#FFD166",
+      "error": "#FF8A8A"
+    },
+    "fonts": {
+      "body": 18,
+      "helper": 16,
+      "section": 22,
+      "title": 26,
+      "menu": 20,
+      "status": 16,
+      "mode": 24,
+      "prop_name": 20,
+      "context_menu": 20
+    },
+    "spacing": { "small": 8, "medium": 12, "large": 16 },
+    "radii": { "control": 8, "panel": 10 },
+    "borders": { "normal": 1, "focus": 2 },
+    "targets": { "button_min_height": 44, "row_min_height": 44, "mode_button_min_height": 56 }
+  },
+  "editors": { "prop": {}, "stickman": {} },
+  "stickman_canvas": {
+    "grid_color": "#FFFFFF26",
+    "selection_core": "#FFFFFF",
+    "selection_halo": "#000000D9"
+  }
+}