feat(members): carve rounded TL/BL on members drawer with 12px void seam to chat and extract VoidGap helper consolidating four per-pane seams

src/app/features/room/MembersDrawer.css.ts

@@ -1,8 +1,18 @@
 import { keyframes, style } from '@vanilla-extract/css';
 import { config, toRem } from 'folds';
+import { VOJO_HORSESHOE_RADIUS_PX } from '../../styles/horseshoe';
 
+// Left edge carves TL + BL the same way `RoomViewProfileSidePanel` does
+// across the 12px horseshoe void gap rendered by Room.tsx — same design
+// language as the page-nav <-> chat split. `overflow: hidden` keeps the
+// rounded corners clean against header / scroll content; the void
+// colour beneath is painted by the parent flex row, not by the panel
+// itself.
 export const MembersDrawer = style({
   width: toRem(266),
+  overflow: 'hidden',
+  borderTopLeftRadius: toRem(VOJO_HORSESHOE_RADIUS_PX),
+  borderBottomLeftRadius: toRem(VOJO_HORSESHOE_RADIUS_PX),
 });
 
 export const MembersDrawerHeader = style({

src/app/features/room/Room.tsx

@@ -38,6 +38,22 @@ type RoomProps = {
   renderRoomView?: (props: { eventId?: string }) => React.ReactNode;
 };
 
+// 12px black seam between the chat column and the right-side pane (profile,
+// media, thread, members). Every active right-side pane renders one of
+// these locally; the parent flex row is painted the same void colour by
+// `Room` so each pane's TL/BL rounded carve can expose the void cleanly.
+function VoidGap() {
+  return (
+    <Box
+      shrink="No"
+      style={{
+        width: toRem(VOJO_HORSESHOE_GAP_PX),
+        backgroundColor: VOJO_HORSESHOE_VOID_COLOR,
+      }}
+    />
+  );
+}
+
 export function Room({ renderRoomView }: RoomProps) {
   const { eventId } = useParams();
   const room = useRoom();
@@ -115,18 +131,40 @@ export function Room({ renderRoomView }: RoomProps) {
   // parent void can't bleed through any transparent slivers.
   const profileOpen = !!useAtomValue(userRoomProfileAtom);
   const mediaOpen = !!useAtomValue(mediaViewerAtom);
+  const callView = room.isCallRoom();
   const showProfileHorseshoe = profileOpen && !isMobile && !showThreadDrawer;
   // Media viewer side pane on desktop — same horseshoe seam idiom
   // as the profile pane. The two are mutually exclusive in practice
   // (the open hooks clear the other atom), so at most one shows at
-  // a time; both feed into `showAnyHorseshoe` for the chat-column
+  // a time; both feed into `paintParentVoid` for the chat-column bg
-  // bg + the void-gap render gate.
+  // and locally gate the shared `<VoidGap />` seam.
   const showMediaHorseshoe = mediaOpen && !isMobile && !showThreadDrawer;
   // Thread drawer side pane on desktop. Mobile hides the chat column
   // entirely (`drawerHidesChat`) so the seam doesn't apply there.
   const showThreadHorseshoe = showThreadDrawer && !isMobile;
-  const showAnyHorseshoe =
+  // Members drawer side pane — mirrors the same horseshoe seam as the
-    showProfileHorseshoe || showMediaHorseshoe || showThreadHorseshoe;
+  // profile/media/thread panes. Gated on the exact same conditions that
+  // mount `<MembersDrawer>` below (group room, desktop, drawer setting on,
+  // no thread overlay, no call surface) so the void gap appears iff the
+  // pane appears.
+  const showMembersHorseshoe =
+    !callView &&
+    !isOneOnOne &&
+    !showThreadDrawer &&
+    screenSize === ScreenSize.Desktop &&
+    isDrawer;
+  // True whenever any right-side pane is mounted. Drives the parent flex
+  // row's void background and the chat column's explicit Background paint
+  // — both prevent the chat-side surface from bleeding through the carved
+  // TL/BL of whichever pane is open. The per-pane `<VoidGap />` decisions
+  // remain local to each render site (a single `paintParentVoid` gate
+  // would over-render when only members is open — there is no
+  // profile/media slot to anchor it to).
+  const paintParentVoid =
+    showProfileHorseshoe ||
+    showMediaHorseshoe ||
+    showThreadHorseshoe ||
+    showMembersHorseshoe;
 
   useKeyDown(
     window,
@@ -152,8 +190,6 @@ export function Room({ renderRoomView }: RoomProps) {
     )
   );
 
-  const callView = room.isCallRoom();
-
   // Disable the atom-driven media viewer when the desktop thread
   // drawer is open — the side-pane mount block below is gated on
   // `!showThreadDrawer`, so the new viewer's right pane wouldn't
@@ -181,7 +217,7 @@ export function Room({ renderRoomView }: RoomProps) {
         <Box
           grow="Yes"
           style={
-            showAnyHorseshoe
+            paintParentVoid
               ? { backgroundColor: VOJO_HORSESHOE_VOID_COLOR }
               : undefined
           }
@@ -191,7 +227,7 @@ export function Room({ renderRoomView }: RoomProps) {
               grow="Yes"
               direction="Column"
               className={
-                showAnyHorseshoe
+                paintParentVoid
                   ? ContainerColor({ variant: 'Background' })
                   : undefined
               }
@@ -213,7 +249,7 @@ export function Room({ renderRoomView }: RoomProps) {
               grow="Yes"
               direction="Column"
               className={
-                showAnyHorseshoe
+                paintParentVoid
                   ? ContainerColor({ variant: 'Background' })
                   : undefined
               }
@@ -245,15 +281,7 @@ export function Room({ renderRoomView }: RoomProps) {
             exclusive via the open hooks. */}
           {!isMobile && !showThreadDrawer && (
             <>
-              {showAnyHorseshoe && (
+              {(showProfileHorseshoe || showMediaHorseshoe) && <VoidGap />}
-                <Box
-                  shrink="No"
-                  style={{
-                    width: toRem(VOJO_HORSESHOE_GAP_PX),
-                    backgroundColor: VOJO_HORSESHOE_VOID_COLOR,
-                  }}
-                />
-              )}
               <RoomViewProfileSidePanel />
               <RoomViewMediaSidePanel />
             </>
@@ -277,21 +305,13 @@ export function Room({ renderRoomView }: RoomProps) {
             screenSize === ScreenSize.Desktop &&
             isDrawer && (
               <>
-                <Line variant="Background" direction="Vertical" size="300" />
+                {showMembersHorseshoe && <VoidGap />}
                 <MembersDrawer key={room.roomId} room={room} members={members} />
               </>
             )}
           {showThreadDrawer && decodedRootId && parentRoomPath && (
             <>
-              {showThreadHorseshoe && (
+              {showThreadHorseshoe && <VoidGap />}
-                <Box
-                  shrink="No"
-                  style={{
-                    width: toRem(VOJO_HORSESHOE_GAP_PX),
-                    backgroundColor: VOJO_HORSESHOE_VOID_COLOR,
-                  }}
-                />
-              )}
               <ThreadDrawer
                 key={`${room.roomId}/${decodedRootId}`}
                 room={room}