(core) Tweak navbar, breadcrumbs, and sign-in buttons

Summary:
The changes are intended to smooth over some sharp edges when a signed-out user
is using Grist (particularly while on the templates site).

Test Plan: Browser tests.

Reviewers: paulfitz

Reviewed By: paulfitz

Differential Revision: https://phab.getgrist.com/D3957

app/client/ui2018/breadcrumbs.ts

@@ -100,10 +100,13 @@ export function docBreadcrumbs(
     isRecoveryMode: Observable<boolean>,
     isSnapshot?: Observable<boolean>,
     isPublic?: Observable<boolean>,
+    isTemplate?: Observable<boolean>,
+    isAnonymous?: boolean,
   }
   ): Element {
+    const shouldShowWorkspace = !(options.isTemplate && options.isAnonymous);
     return cssBreadcrumbs(
-      dom.domComputed<[boolean, PartialWorkspace|null]>(
+      !shouldShowWorkspace ? null : dom.domComputed<[boolean, PartialWorkspace|null]>(
         (use) => [use(options.isBareFork), use(workspace)],
         ([isBareFork, ws]) => {
           if (isBareFork || !ws) { return null; }