Removing a friend's Bot is silent and irreversible: no confirm/undo, re-invite fails with raw 'relationship_exists' #139

Environment: ThinkFlowLab/FlyBot main 1ac7104 (core, plugins/social, plugins/tree) on @deepseek-ai/dsh@0.2.0-rc.2, two fresh installs on one Linux box (A on :3080, B on :3081), Bot Social server https://47-80-69-220.sslip.io. Found in the scheduled two-instance UI self-test on 2026-10-16 (~19:35 UTC+8).

What happened

1. On B, Friends' Bots → SelfA1935 → "Helper · SelfA1935's Bot" → × ("Remove this Bot"). It disappears immediately, with no confirmation and no undo. The friend row stays with "No Bots shared yet".
2. There is no way back. Re-opening the same invite link gives Joining failed: Bot Social join_invite: invite is used. A fresh invite from A (Helper → Invite to this Bot → Create another invite link) gives Joining failed: Bot Social join_invite: relationship_exists. A has no "share again" for an existing friend.
3. A still sees the grant in Helper → Manage access ("Chief@chief.selfb1935.home / Revoke"), so A thinks B has Helper and B thinks it is gone.

Repro

1. A invites B to Helper; B accepts.
2. B clicks × on Helper.
3. B: + → Accept invite with the old link, then with a new link from A.

Expected

• Remove asks once ("Remove Helper? SelfA1935 can share it again.") or offers Undo in the toast.
• Removing is a real revoke (or at least visible to A), so both sides agree on who has access.
• A new invite to an existing friend just re-grants that Bot (no relationship_exists), or B has a "Show hidden Bots" path.
• Errors are plain English, not raw tool output ("This invite was already used. Ask SelfA1935 for a new one.").

Code pointer (hunch, verify)

Remove is the local hide from #90 (hidden-remotes.js): the hide is only forgotten after the grant disappears, so a still-granted Bot can never come back on B.