fix(ui): flush playlist context submenus to parent row (#713)

* fix(ui): place playlist context submenus flush to trigger row

Use left/right/top 100% instead of calc(100% + 4px) so there is no dead
gap when moving the pointer from Add to playlist into the submenu.

* fix(ui): defer closing playlist submenu on trigger mouseleave

Use a short timer and :hover on the trigger row so slow moves across
border/subpixel gaps still reach the nested submenu; cancel timer on
re-enter and when the context menu closes.

src/components/contextMenu/QueueItemContextItems.tsx

@@ -16,7 +16,8 @@ export default function QueueItemContextItems(props: ContextMenuItemsProps) {
     playTrack, playNext, enqueue, removeTrack, queue, currentTrack, closeContextMenu,
     starredOverrides, setStarredOverride, lastfmLovedCache, setLastfmLovedForSong,
     openSongInfo, userRatingOverrides, setKeyboardRating, keyboardRating,
-    playlistSubmenuOpen, setPlaylistSubmenuOpen, playlistSongIds, setPlaylistSongIds,
+    playlistSubmenuOpen, setPlaylistSubmenuOpen, cancelPlaylistSubmenuCloseTimer, onPlaylistSubmenuTriggerMouseLeave,
+    playlistSongIds, setPlaylistSongIds,
     orbitRole, entityRatingSupport, audiomuseNavidromeEnabled,
     applySongRating, applyAlbumRating, applyArtistRating,
     handleAction, startRadio, startInstantMix, downloadAlbum, copyShareLink, isStarred,
@@ -42,8 +43,8 @@ export default function QueueItemContextItems(props: ContextMenuItemsProps) {
               <div
                 className={`context-menu-item context-menu-item--submenu ${playlistSubmenuOpen && playlistSongIds[0] === song.id ? 'active' : ''}`}
                 data-playlist-trigger-id={song.id}
-                onMouseEnter={() => { setPlaylistSongIds([song.id]); setPlaylistSubmenuOpen(true); }}
-                onMouseLeave={() => setPlaylistSubmenuOpen(false)}
+                onMouseEnter={() => { cancelPlaylistSubmenuCloseTimer(); setPlaylistSongIds([song.id]); setPlaylistSubmenuOpen(true); }}
+                onMouseLeave={onPlaylistSubmenuTriggerMouseLeave}
               >
                 <ListMusic size={14} /> {t('contextMenu.addToPlaylist')}
                 <ChevronRight size={13} style={{ marginLeft: 'auto' }} />