feat(calls): live-call dot on the space rail (#148)

A small red dot on a space tab when any room in that space (recursively)
has an active MatrixRTC session, so a live call is visible even when you
are looking at a different space or your DMs. Hidden while the space is
selected — the room list already shows the Live badge there.

Co-Authored-By: Claude Opus 5 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01PPmy3tPq869XDW4njjVaKA

src/app/pages/client/sidebar/SpaceTabs.css.ts

@@ -0,0 +1,16 @@
+import { style } from '@vanilla-extract/css';
+import { color, toRem } from 'folds';
+
+/** [Gitea #148] Bottom-right live-call dot on a space tab. */
+export const LiveDot = style({
+  position: 'absolute',
+  right: toRem(-2),
+  bottom: toRem(-2),
+  width: toRem(10),
+  height: toRem(10),
+  borderRadius: '50%',
+  backgroundColor: color.Critical.Main,
+  boxShadow: `0 0 0 ${toRem(2)} ${color.Background.Container}`,
+  pointerEvents: 'none',
+  zIndex: 1,
+});

src/app/pages/client/sidebar/SpaceTabs.tsx

@@ -47,6 +47,8 @@ import {
 import { useMatrixClient } from '../../../hooks/useMatrixClient';
 import { roomToParentsAtom } from '../../../state/room/roomToParents';
 import { allRoomsAtom } from '../../../state/room-list/roomList';
+import { useAnyRoomLiveCall } from '../../../hooks/useSpaceLiveCall';
+import { LiveDot } from './SpaceTabs.css';
 import {
   getOriginBaseUrl,
   getSpaceLobbyPath,
@@ -450,6 +452,15 @@ function SpaceTab({
 
   const [menuAnchor, setMenuAnchor] = useState<RectCords>();
 
+  // [Gitea #148] Subtle live-call dot for a space you're not looking at.
+  const roomToParentsForLive = useAtomValue(roomToParentsAtom);
+  const liveChildren = useSpaceChildren(
+    allRoomsAtom,
+    space.roomId,
+    useRecursiveChildScopeFactory(mx, roomToParentsForLive),
+  );
+  const liveCall = useAnyRoomLiveCall(liveChildren);
+
   const handleContextMenu: MouseEventHandler<HTMLButtonElement> = (evt) => {
     evt.preventDefault();
     const cords = evt.currentTarget.getBoundingClientRect();
@@ -497,6 +508,14 @@ function SpaceTab({
               <UnreadBadge highlight={unread.highlight > 0} count={unread.total} />
             </SidebarItemBadge>
           )}
+          {liveCall && !selected && (
+            <span
+              className={LiveDot}
+              role="img"
+              aria-label="A call is live in this space"
+              title="A call is live in this space"
+            />
+          )}
           {menuAnchor && (
             <PopOut
               anchor={menuAnchor}