zebra-spaces: mobile thumbs span full viewport row instead of 2-up columns

web/zebra-spaces.html

@@ -239,7 +239,10 @@
     .cameras-col { grid-row: 3;
                    border-right: none; border-top: 1px solid #ddd;
                    padding-right: 0; padding-top: 1rem; }
-    #tiles-thumbs { grid-template-columns: repeat(auto-fill, minmax(180px, 1fr)); }
+    /* on mobile each thumb takes a full row — a phone viewport is
+     * narrow enough that splitting into 2 columns of ~200px ends up
+     * smaller than just stacking. */
+    #tiles-thumbs { grid-template-columns: minmax(0, 1fr); }
   }
   /* never let dynamically-appended <audio> sinks (one per remote
    * speaker) render their default ~300px control strip — they're just
@@ -3781,8 +3784,8 @@ logLine('', 'ready — pick a handle, type a rendezvous code, enter the space');
 
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