Admin @ work-dispatch still opens group rounds instead of board assign + task-drive wake #1254

Observed (prod tip 7fdb8082, 交付组 seq 3112–3171)

#1185/#1205 intended: assign/claim/progress/handoff via track_tasks; assignee wakes in own chat, not a group round.

Live trajectory after those tips are on prod:

• Chief (admin) 34/60 messages; longest consecutive admin run 9 messages, almost all @Dev4 / @Reviewer / @Reviewer2 with full tip audits, rebase instructions, and "don't judge this head" essays.
• Board cards exist and get updated, but verbal @ dispatch is still the control plane; members answer in the group, so the room stays a status meeting.
• A pull queue: the lead enqueues work, an idle member of the role claims it #1247 (pull queue) is complementary product intent from the owner the same day — this issue is the host gap that lets admin chat keep bypassing board-driven wakes.

Desired

For a group room in mode: admin (or any room with an open board):

1. When the admin (or task lead) posts an @ to a member that is clearly an assign/handoff (issue/PR id + imperative), the host should prefer track_tasks assign/update + task-drive DM wake, and not start a multi-turn group round for that member.
2. If a card for that work already exists, update it; don't require a parallel novel in chat.
3. Keep true questions to a person (needs a human decision) as group turns.

Hypothesis only (verify in code): today any @ still schedules ROOM_REPLY / room parts even when a board card covers the assignee — #1204's boardCoversCue helps silence covered cues, but admin new instructions that only share a title still open rounds, and admin is rewarded for putting the whole brief in chat.

Acceptance

• Test: admin @Dev #1234 rebase and push with/without an existing card → card written/updated, Dev woken via task-drive, no Dev group part (or only a one-line ack path).
• A human @Chief 现在token… style ask still gets a normal admin group turn.
• Related: Let one task lead assign group cards and start the assignee in the group #1185/Board-driven continuous execution: assign/claim/progress/handoff via track_tasks #1205 (closed), A pull queue: the lead enqueues work, an idle member of the role claims it #1247 (queue UX).

Evidence

Prod dump seq 3112–3171; Chief @-chain around #1221 / #1240 / #1226 same morning.