Refresh channel tree after volume changes

Tree items render a display string snapshotted at build time, so
changing a user's volume updated the gain but left the stale
percentage on screen. Rebuild the tree and refresh after volume
change and reset, matching what the mute hotkeys already do.

Co-Authored-By: Claude Opus 5 <noreply@anthropic.com>

ui_tree.go

@@ -38,7 +38,7 @@ func (ti TreeItem) TreeItemStyle(fg, bg uiterm.Attribute, active bool) (uiterm.A
 }
 
 func (b *Barnard) changeVolume(users []*gumble.User, change float32) {
-	b.withStream(func(stream *gumbleopenal.Stream) {
+	changed := b.withStream(func(stream *gumbleopenal.Stream) {
 		for _, u := range users {
 			var boost uint16
 			var ng float32
@@ -63,10 +63,13 @@ func (b *Barnard) changeVolume(users []*gumble.User, change float32) {
 			b.AddOutputLine("Volume: could not save setting: " + err.Error())
 		}
 	})
+	if changed {
+		b.refreshVolumeDisplay()
+	}
 }
 
 func (b *Barnard) resetVolume(users []*gumble.User) {
-	b.withStream(func(stream *gumbleopenal.Stream) {
+	changed := b.withStream(func(stream *gumbleopenal.Stream) {
 		for _, u := range users {
 			// Reset to original volume (1.0) and boost (1)
 			u.SetBoost(uint16(1))
@@ -78,6 +81,16 @@ func (b *Barnard) resetVolume(users []*gumble.User) {
 			b.AddOutputLine("Volume: could not save setting: " + err.Error())
 		}
 	})
+	if changed {
+		b.refreshVolumeDisplay()
+	}
+}
+
+// Tree items render a display string snapshotted at build time, so a volume
+// change is only visible after the tree is rebuilt.
+func (b *Barnard) refreshVolumeDisplay() {
+	b.RebuildUserChannelTreePreservingSelection()
+	b.Ui.Refresh()
 }
 
 func makeUsersArray(users gumble.Users) []*gumble.User {