Add tests for scenery surface caching and preview behavior

- Introduced `test_scenery_brick_preview.gd` to validate focused placement and CPU draw-cost for large brick walls.
- Added `test_scenery_surface_cache.gd` to assess texture budget, visual equivalence, and cache invalidation.
- Created `test_scenery_surface_preview.gd` to evaluate adaptive preview selection and placement behavior.
- Implemented various helper functions to measure drawing performance and validate expected behaviors during tests.
- Added unique identifiers for new test files to ensure proper tracking and management.

sandbox_theme.json

@@ -114,13 +114,57 @@
       "surface_color_picker_min_size": [320, 340],
       "action_min_target_size": 48
     },
+    "confirmation": {
+      "scenery_erase_size": [520, 208],
+      "padding": 18,
+      "body_gap": 10,
+      "footer_gap": 12,
+      "corner_radius": 16,
+      "border_width": 2,
+      "title_font_size": 26,
+      "message_font_size": 20,
+      "button_font_size": 20,
+      "button_height": 48,
+      "button_radius": 12,
+      "button_border_width": 2,
+      "remove_button_width": 170,
+      "keep_button_width": 132,
+      "surface_color": "#202633FA",
+      "border_color": "#22C6FF",
+      "accent_color": "#22C6FF",
+      "action_color": "#087DBA",
+      "danger_color": "#FF626B",
+      "danger_hover_surface": "#3B252C",
+      "danger_pressed_surface": "#4A252D"
+    },
     "asset_selector": {
       "backdrop_alpha": 0.55,
       "cell_size": [190, 220],
       "thumbnail_size": [156, 156],
       "surface_preview_size": [420, 132],
       "look_cue_size": [80, 42],
-      "setup_gap": 10
+      "setup_gap": 8,
+      "setup_title_size": 30,
+      "setup_heading_size": 26,
+      "setup_choice_font_size": 22,
+      "setup_choice_height": 68,
+      "setup_choice_corner_radius": 22,
+      "setup_choice_border_width": 2,
+      "tab_font_size": 22,
+      "tab_height": 60,
+      "filter_chip_font_size": 20,
+      "filter_chip_height": 48,
+      "filter_chip_gap": 8,
+      "setup_button_font_size": 20,
+      "button_border_width": 2,
+      "footer_gap": 16,
+      "surface_corner_radius": 14,
+      "look_corner_radius": 8,
+      "corner_radius": 16,
+      "compact_swatch_size": 42,
+      "color_group_gap": 8,
+      "action_color": "#087DBA",
+      "separator_color": "#AAB2C0A0"
     }
   },
   "palette": {
@@ -185,7 +229,13 @@
       "close_width": 88,
       "surface_color": "#171B24",
       "hover_surface": "#303A4B",
-      "selected_surface": "#12394A"
+      "selected_surface": "#12394A",
+      "primary_color": "#087DBA",
+      "primary_hover_color": "#1596D3",
+      "primary_pressed_color": "#066B9F",
+      "destructive_color": "#FF626B",
+      "destructive_hover_surface": "#3B252C",
+      "destructive_pressed_surface": "#4A252D"
     },
     "prop": {
       "stickman_cue_color": "#F5F7FA",