Social startup: fresh install fails on a taken handle (default displayName 'FlyBot'), and my own handle is never shown #136

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. A fresh install whose flybot-social config uses a display name that already exists on the server does not start Social. With the config default (displayName unset → FlyBot → @flybot.home), every install after the first one on a server hits this. Log: flybot-social: start failed: Bot Social onboarding failed: HTTP 409 (handle @boxa.home is taken). Change displayName in the flybot-social config so a new home is created, then restart.
2. When registration does succeed, the UI never shows my own identity. On both instances the social sidebar shows only "Chief", "Friends' Bots 0" and the empty-state hint; there is no "@selfa1935.home" or "Connected to Bot Social" anywhere. I only learn my own handle when a friend sees it.

Repro

1. Install the plugins into a fresh DSH_HOME and set flybot-social.config.displayName to a name another install already used (or leave it unset when anyone has already onboarded as FlyBot).
2. Start dsh. Social does not start; the user has to edit YAML and restart.
3. With a unique name: start, open the UI, look for your own handle / connection state.

Expected (owner design: automatic registration at startup, no manual step)

• Onboarding never needs a hand-edited config: on a handle conflict pick a free handle automatically (e.g. @flybot-2.home or a short suffix), or let the user choose one in the UI, and continue.
• The social sidebar shows one short line with my own handle and connection state (e.g. a small "@selfa1935.home" under the section, with a copy action), so I can tell it's working and tell friends who I am.

Code pointers (hunch, verify)

plugins/social/src/social.js onboard() / onboardError() turn 409 into a fatal start error; startSocial defaults displayName ?? 'FlyBot'.