Attention watermark + return-from-away briefing ("brief me")

[heavygee]

Goal

Let the operator ask the Overseer "brief me" / "what changed since I was last here?" and get a synthesized return-from-away fleet briefing — deltas since last attention + current blockers/decisions + recommended focus. The near-term, trackable primitive is a per-operator last-seen watermark + since-last-seen delta over the event stream; the briefing interaction rides the nascent Overseer (#25).

Spec

• docs/plans/2026-06-05-overseer-rollout-and-diagrams.md §5 (return-from-away briefing)
• docs/plans/2026-06-03-overseer-prioritization.md §9 (the briefing is the digest's content, minus the schedule)
• The per-session "Greet me / Brief me" precedent (discussion Voice roadmap: picker -> provider abstraction -> local stack -> fleet command centre tiann/hapi#691 dogfooding notes) — this is the fleet-level "Brief me"
• docs/chad-operator-overseer-chat.md ("3 agents finished. Two routine. One needs your decision…")

Why not scrum, why no schedule

• Scrum standup ceremony (per-agent roll-call, fixed daily time) is meatspace baggage — humans schedule standups because they need to converge. An agent fleet does not. Scheduling dropped entirely.
• Adopt the scrum function, not the ritual: deltas-since-last + current blockers + recommended focus, SYNTHESIZED, never a per-agent roll-call (a roll-call is the "narrating log file" failure mode at standup scale).
• Trigger = operator-initiated ("brief me") + attention-gap (return after being away > N). Not clock-driven. "Day start" is the wrong boundary; "return from away" is the right one (could be morning or after a 2-hour meeting).

Acceptance

• Near-term primitive (can land with the inbox substrate): record a per-operator last_seen_at / attention watermark, and support a since-last-seen delta query over events/inbox (done-while-away, newly-blocked, resolved-while-away, new-since-last).
• Briefing interaction (rides Step 3: Read-only Overseer wired to voice #25): on operator-initiated "brief me" or a detected return-from-away, produce a synthesized briefing — deltas + blockers/decisions + recommended focus order. Not an enumeration.
• No scheduled/clock-driven standup — operator-initiated + attention-gap only.
• Second consumer falls out for free: "what did you handle while I was away?" — audit of auto-resolved/dispatched items against the same watermark.

Out of scope

• Scheduled/recurring standup (rejected — meatspace convergence artifact).
• Learned salience in the briefing (coarse rank from Step 2.5: Inbox substrate + dumb v1 ordering + operator-action logging #23 only).
• Voice specifics — the briefing reads over Step 3: Read-only Overseer wired to voice #25's surface (voice or text); not a separate voice feature.

Dependencies

• Watermark + delta primitive: blocked by Step 2: Events table + worker emission #22 (events), Step 2.5: Inbox substrate + dumb v1 ordering + operator-action logging #23 (inbox)
• Briefing interaction: blocked by Step 3: Read-only Overseer wired to voice #25 (nascent read-only Overseer)
• Relates to: prioritization §9 (digest mode), UX: TL;DR-first response rendering with expand-to-full setting #9 (TL;DR rendering reuse), the attention-inbox pane
• Part of: Fleet Overseer architecture — umbrella #19

Notes

The briefing is the narrative front-end of the attention queue at a return-from-away boundary — same data as the inbox, different intent from the "what's next?" single-item query. "What's next?" is pull-one (Brazil bang-bang); "brief me" is orient-all-with-deltas. Keep both; don't merge.