Make the viewport label size one setting

Scene labels used `small` (11 px), the Texture tab used `body` (13 px). Both now
read `Theme.viewportLabelSize` through two tokens that differ only in colour.

Dropping the per-frame `label.style.fill` assignment matters: textStyle() returns
shared cached instances, so with both views on one token it would have recoloured
the scene labels too.

Co-Authored-By: Claude Opus 5 <noreply@anthropic.com>

src/ui/Theme.ts

@@ -6,6 +6,7 @@ export const Theme = {
   monoFont: '"JetBrains Mono", Consolas, "Courier New", monospace',
   fontSize: 13,
   smallFontSize: 11,
+  viewportLabelSize: 10,
   rowHeight: 26,
   controlHeight: 24,
   padding: 8,
@@ -62,7 +63,16 @@ export const Theme = {
 
 const styleCache = new Map<string, TextStyle>();
 
-export type TextStyleToken = 'body' | 'bodyBold' | 'muted' | 'small' | 'title' | 'mono' | 'accent';
+export type TextStyleToken =
+  | 'body'
+  | 'bodyBold'
+  | 'muted'
+  | 'small'
+  | 'title'
+  | 'mono'
+  | 'accent'
+  | 'viewportLabel'
+  | 'viewportLabelMuted';
 
 /** Shared TextStyle instances so Pixi can cache glyph measurements per token. */
 export function textStyle(token: TextStyleToken = 'body'): TextStyle {
@@ -97,6 +107,12 @@ export function textStyle(token: TextStyleToken = 'body'): TextStyle {
     case 'accent':
       style = new TextStyle({ ...base, fill: Theme.colors.accentText, fontWeight: '600' });
       break;
+    case 'viewportLabel':
+      style = new TextStyle({ ...base, fontSize: Theme.viewportLabelSize });
+      break;
+    case 'viewportLabelMuted':
+      style = new TextStyle({ ...base, fontSize: Theme.viewportLabelSize, fill: Theme.colors.textMuted });
+      break;
   }
   styleCache.set(token, style);
   return style;