Team group: assign PRs to members’ Bots (GitHub truth, group as write entry) #427

Child of #149. Related: #349, #55, #408, #51.

Scenario (first slice)

Several people’s Bots join one team group. A team admin assigns a PR to someone’s Bot from the group. People should not have to edit GitHub by hand.

Design choice: C′

• Source of truth: GitHub PR assignee / labels.
• Write entry: the team group. Admin says “give PR #N to @person’s Bot” → FlyBot updates GitHub assignee/label, then that Bot may work.
• Read path: Bots and the group follow GitHub state (webhook preferred over poll). Group also broadcasts progress and the conclusion.
• Not chosen for Now: chat-as-board only (A), or a separate task-card system as truth (B).

Acceptance

1. Admin assigns in the group → PR on GitHub shows the matching assignee (or agreed label).
2. Only the assigned person’s Bot picks up that PR; others do not race it.
3. Reassign in the group updates GitHub and the previous Bot stops / unlocks ([Team] Recover task handoffs without duplicate work #55 / RFC: multi-Bot × GitHub — PR budget, task lock, decision card (not a new Git) #408).
4. Progress and final conclusion are visible in the group thread; GitHub remains the audit trail for who owns the PR.

Out of scope

Full Magpie-style routing UI; personal-edition complexity; replacing Git.

Open questions

1. Assignee = human GitHub user, or a Bot identity / label such as bot:<name>?
2. Who may reassign: team admin only, or also the current owner?
3. Stuck Bot: timeout then auto-release, or admin-only reclaim?

Process: OpenCode + Codex review.