feat(chat): bypass-list UI for discuss/work channels

- create-channel modal: optional bypass multi-select (discuss/work only),
  sent as bypassUserIds; reset on open/close.
- members panel (in-channel, discuss/work): bypass members tagged
  'bypass'; others get a '→ bypass' action -> POST /channels/:id/bypass.
- loadChannelMembers consumes the new {userId,bypass} member shape.

Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>

src/index.css

@@ -145,6 +145,13 @@ button {
 .btn-secondary:hover {
   background: #44474f;
 }
+.btn-xs {
+  padding: 2px 8px;
+  font-size: 11px;
+  line-height: 1.4;
+  white-space: nowrap;
+  flex: 0 0 auto;
+}
 .btn-ghost {
   background: transparent;
   color: var(--text-muted);