Website: Preserve the mode query arg when opening OPFS site (#63)

When opening a non-temporary site, Playground removes all the query args
from the URL to avoid running boot flows again, e.g. preserving
`?blueprint-url=` would confuse the user at best, and corrupt the site
at worst. Problem is, some query args are useful to preserve. For
example, `mode=seamless` hides the "browser UI" and it's confusing when
Playground immediately drops it from the URL.

This PR preserves three benign query args:

* mode
* networking
* login (which only sets a PHP const these days)

 ## Testing instructions

* Create a new OPFS site
* Open it
* Add
?mode=seamless&networking=yes&login=yes&blueprint-url=https://mysite.com/blueprint.json
to the URL
* Confirm the first three query args were preserved and the
blueprint-url was dropped

Author: adamziel

packages/playground/website/src/lib/state/url/router.ts

@@ -41,8 +41,16 @@ export class PlaygroundRoute {
 		if (site.metadata.storage === 'none') {
 			return updateUrl(baseUrl, site.originalUrlParams || {});
 		} else {
+			const baseParams = new URLSearchParams(baseUrl.split('?')[1]);
+			const preserveParamsKeys = ['mode', 'networking', 'login', 'url'];
+			const preserveParams: Record<string, string | null> = {};
+			for (const param of preserveParamsKeys) {
+				if (baseParams.has(param)) {
+					preserveParams[param] = baseParams.get(param);
+				}
+			}
 			return updateUrl(baseUrl, {
-				searchParams: { 'site-slug': site.slug },
+				searchParams: { 'site-slug': site.slug, ...preserveParams },
 				hash: '',
 			});
 		}