[techdocs/cli] Use light theme if it's not dark, to avoid breaking the theme selector on other values in local storage

Fixes #12995

Signed-off-by: Axel Hecht <axel@pike.org>

.changeset/purple-games-think.md

@@ -0,0 +1,5 @@
+---
+'techdocs-cli-embedded-app': patch
+---
+
+Theme selector in `npx @techdocs/cli serve` would break if localstorage had a non-light-or-dark value for theme.

packages/techdocs-cli-embedded-app/src/components/TechDocsPage/TechDocsPage.tsx

@@ -55,7 +55,7 @@ export const TechDocsThemeToggle = () => {
   const appThemeApi = useApi(appThemeApiRef);
   const classes = useStyles();
   const [theme, setTheme] = useState<Themes>(
-    (appThemeApi.getActiveThemeId() as Themes) || Themes.LIGHT,
+    appThemeApi.getActiveThemeId() === Themes.DARK ? Themes.DARK : Themes.LIGHT,
   );
 
   const themes = {