feat(web): open spaces as a plain chat on phones with a side drawer

Spaces, channels, files, members and the account move into a left drawer,
the top bar keeps only the essentials, and touch devices get a tap menu
instead of always-visible delete buttons. Also fixes the history checkboxes
in the channel settings sheet.

web/src/features/channel/Workspace.module.css

@@ -65,38 +65,11 @@
   padding-inline: env(safe-area-inset-left) env(safe-area-inset-right);
 }
 
-.mobile .navigation {
-  max-height: 30dvh;
-  flex-shrink: 0;
-  border-right: 0;
-}
-
 .mobileContent {
   flex: 1;
   overflow: hidden;
 }
 
-.tabs {
-  display: flex;
-  flex-shrink: 0;
-  border-bottom: 1px solid var(--line);
-}
-
-.tabs button {
-  flex: 1;
-  min-height: 44px;
-  border: 0;
-  background: var(--surface);
-  color: var(--text-dim);
-  font: inherit;
-  cursor: pointer;
-}
-
-.tabs button[aria-pressed="true"] {
-  border-bottom: 2px solid var(--accent);
-  color: var(--text);
-}
-
 .pendingCatalog {
   padding: var(--space-2) var(--space-3);
   border-top: 1px solid var(--line);