A face-room invite preview says "A room with no name" for every room FlyBot creates #859

What is wrong

The invite preview card's title line reads A room with no name whenever Bot Social has no name for the room, which is every room created from FlyBot.

• plugins/social/client.js:1532 — preview.name || 'A room with no name'.
• The server's preview answer for these rooms carries "name": null (measured on social.botawaken.com in Face-room invite preview renders the room lead as "object Object" #846), and previewInvite maps that to '' (plugins/social/src/face-rooms.js:699).
• Nothing in this repo sends a name to Bot Social: a room is opened with POST /v1/face-rooms/join and a body of { code, bots } (face-rooms.js:721) — there is no name field. FlyBot's own title (formatFaceRoomTitle, plugins/social/src/face-title.js, e.g. Face-to-face · SelfTest A2, SelfTest B2 · 988036) is generated locally and never goes on the wire.

So the card reads:

A room with no name
Lead: Chief (SelfTest A2)
2 / 8 in the room
9:53 left to join

The other three lines are right; the first one reports the absence of a name as if something broke, which is the first thing a person sees before deciding to join.

Expected

When the server has no name, the title line names what kind of room it is instead of reporting a missing field. The wording settled on here is Face-to-face room:

Face-to-face room
Lead: Chief (SelfTest A2)
2 / 8 in the room
9:53 left to join

The Lead: line and the count are what actually identify the room to the person joining, and both already work (#846 fixed the lead). Nothing else about the card changes.

Do not invent a name from the ticket: the ticket is opaque, and the local title cannot be rebuilt on the invited side — that home has no member list and no room code.

Scope

• plugins/social/client.js:1532 — the fallback string only.
• plugins/social/test/social.test.js — the preview-card cases around :9200-9254 already assert face-link-preview-name for a named room (Kitchen sync). Add the empty-name case: the server answers name: '', and the card draws Face-to-face room.
• One changelog.d/ fragment, Fixes #<this>.

Acceptance

1. A preview whose answer has name: '' (and one with name: null) draws Face-to-face room, not A room with no name.
2. The existing named-room case still draws its name unchanged (Kitchen sync), and the Lead: / n / 8 in the room / expiry lines are untouched.
3. The literal A room with no name no longer appears anywhere in plugins/social/.
4. Negative control: restoring the old literal reds only the empty-name case, and the named-room case stays green.

Not this issue

• Showing the real generated title needs the name to travel to Bot Social (store a name with the room, or hand back the code and members so a title can be rebuilt). That is a ThinkFlowLab/bot-social change and is out of scope here. The same wall exists for local-room links (A local room has no invite of its own: no link to hand over, only a picker of Bots the account already knows #852).
• Lead: object Object was Face-room invite preview renders the room lead as "object Object" #846, fixed in fix(social): name the invite lead from the member object #849.