Face-to-face: stale active room cards (peer left / ended) should move to Past rooms automatically #129

Found in a two-instance UI retest of the social plugin (two box instances, main e884312; source checked on 649bebe).

Observed

Face-to-face rooms keep stale active cards:

1. After the peer leaves, the other side's sidebar still shows the room as open with a Leave button, although the chat already says "BoxB's Chief left".
2. A room whose matching window ended shows an ended chip with a Leave button in the active area, on both sides. It never moves to Past rooms by itself.

Expected

• No stale active card: once the room is over (peer left / window ended / server says closed) it moves to Past rooms automatically, with a single Open button, on both sides.
• The chip and the buttons always match the state the chat shows.

Repro

1. Two instances, join the same 6-digit room with one Bot each, Enter chat.
2. Peer clicks Leave. The remaining side's sidebar still says open + Leave.
3. Separately: start a room and let the matching window expire. The card shows ended + Leave under the active rooms.

Likely cause

• plugins/social/client.js: isPastFace(room) is only status === 'closed' || 'left', while faceChip(room) can return 'ended' for a candidate room whose expiresAt passed. That room is treated as active and renders Leave (FaceRoomCard). Fix idea: treat expired candidates as past (or have the host flip their status).
• plugins/social/src/social.js applyFaceSnapshot / pollFaceRooms: a member.left event is only posted as a notice (postNotice); nothing updates the room status when the peer leaves or the room closes, and the room only moves to pastFaceRooms from leaveFaceRoom (the user's own click). Fix idea: when a snapshot says closed/ended/no other live members, call rememberPastFace and drop the active entry.

Product note: usability and simplicity are an explicit owner priority for this plugin: few buttons, short copy, short click paths. Please prefer removing or merging UI over adding more.