Add reusable UI components for Phase 7 UI Polish

- Introduced `EmojiQuickGrid`, `FontPresetPicker`, and `PresetSizeToggle` classes for emoji selection, font presets, and size toggles respectively.
- Implemented configuration methods for each component to handle dynamic content and theming.
- Created tests for the new components to ensure functionality and integration with the existing UI.
- Added a comprehensive architecture specification for Phase 7 UI Polish detailing scope, implementation, and validation strategies.
- Updated existing theme handling to support new UI elements and ensure consistent styling across the application.

scripts/stage_spawner.gd

@@ -63,6 +63,18 @@ func get_spawnable_ids() -> Array[String]:
 	return ids
 
 
+## UI-safe registry view. Callers receive no templates or mutable registry state.
+func get_palette_entries() -> Array[Dictionary]:
+	var icons: Dictionary = {"ground":"🧱", "ramp":"📐", "step":"🪜", "prop":"📦", "stickman":"🧍", "area":"🎯"}
+	var categories: Dictionary = {"terrain":"Terrain", "prop":"Props", "stickman":"Cast", "area":"Events"}
+	var result: Array[Dictionary] = []
+	for entry: Dictionary in _registry:
+		var id: String = String(entry.get("id", ""))
+		var kind: String = String(entry.get("kind", ""))
+		result.append({"placement_id":id, "kind":kind, "label":String(entry.get("label", id)), "icon":String(icons.get(id, "")), "category":String(categories.get(kind, "")), "opens_selector":kind == "prop" or kind == "stickman"})
+	return result
+
+
 func get_label(id: String) -> String:
 	var entry := _find_entry(id)
 	return String(entry.get("label", id)) if not entry.is_empty() else id