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/MobileTopBar.module.css

@@ -0,0 +1,62 @@
+.bar {
+  position: sticky;
+  top: 0;
+  z-index: 10;
+  display: flex;
+  flex-shrink: 0;
+  align-items: center;
+  gap: var(--space-1);
+  min-height: var(--bar-h);
+  padding: 0 var(--space-2);
+  padding-top: env(safe-area-inset-top);
+  border-bottom: 1px solid var(--line);
+  background: var(--glass);
+  /* stylelint-disable-next-line property-no-vendor-prefix */
+  -webkit-backdrop-filter: var(--blur-bar);
+  backdrop-filter: var(--blur-bar);
+}
+
+.raw {
+  border-bottom-color: var(--warn);
+}
+
+.title {
+  flex: 1;
+  min-width: 0;
+  margin: 0;
+  overflow: hidden;
+  font-size: 16px;
+  font-weight: 600;
+  text-overflow: ellipsis;
+  white-space: nowrap;
+}
+
+.lock {
+  display: inline-flex;
+  color: var(--ok);
+}
+
+.warn {
+  padding: 1px var(--space-2);
+  border-radius: var(--radius-sm);
+  background: var(--warn-soft);
+  color: var(--warn);
+  font-size: 12px;
+}
+
+.conn {
+  font-size: 12px;
+}
+
+.reconnecting {
+  color: var(--busy);
+}
+
+.offline {
+  color: var(--danger);
+}
+
+.active {
+  background: var(--accent-soft);
+  color: var(--busy);
+}