feat(theme): game_theme.tres (fonts + stylebox variations) via builder

client/scripts/theme/theme_keys.gd

@@ -0,0 +1,30 @@
+# client/scripts/theme/theme_keys.gd
+class_name ThemeKeys
+extends RefCounted
+## Type-variation names for game_theme.tres. Scripts set `theme_type_variation`
+## to one of these so a typo is a compile-time symbol error, not a silent miss.
+## §2: presentation.
+
+const PRIMARY_CTA := &"PrimaryCTA"
+const TAB := &"Tab"
+const TAB_ACTIVE := &"TabActive"
+const CHIP := &"Chip"
+const ITEM_TILE := &"ItemTile"
+const ITEM_TILE_EMPTY := &"ItemTileEmpty"
+const PARCHMENT_CARD := &"ParchmentCard"
+const PARCHMENT_INSET := &"ParchmentInset"
+const DARK_PANEL := &"DarkPanel"
+
+## Every variation name + the base Control type it decorates. The builder and the
+## test both iterate this so they can never drift apart.
+const ALL := {
+	PRIMARY_CTA: "Button",
+	TAB: "Button",
+	TAB_ACTIVE: "Button",
+	CHIP: "Button",
+	ITEM_TILE: "PanelContainer",
+	ITEM_TILE_EMPTY: "PanelContainer",
+	PARCHMENT_CARD: "PanelContainer",
+	PARCHMENT_INSET: "PanelContainer",
+	DARK_PANEL: "PanelContainer",
+}