Tracer: Overview shows today Channel activity and sender breakdown #703

Parent and design

Parent: #541. Related Activity Center / Human Inbox specification: #126. Follow ADR-0098 and the Human-approved Channel-total plus sender-detail scenario; #424 already delivered the committed Channel message-count authority.

User behavior

In Activity Center → Overview, the Human can compare today's message activity across their Bot DMs and Groups, then expand one Channel to see who sent how many messages. The active Bot/action cards remain available in the same view.

Acceptance

• Show today's committed message total per Human-accessible Channel, with Human / Bot segments and numeric counts. If other committed author kinds exist, label their separate remainder so the displayed total remains exact.
• Expand a Channel row to show each current sender name / kind and today's count. Human labels resolve in that source Channel; PersonaBot labels use the current registry. Provide navigation to the Channel.
• Count distinct committed Source Events per Channel, never Bot Admissions or generated attention notices. A message admitted to several Bots contributes one message to its Channel.
• Use the Host's local calendar day, display that day and timezone, and exclude messages outside its start/end boundary. Respect Human membership visibility, including history before a member's visible revision; exclude deleted Channels and Bot-to-Bot DMs.
• Existing empty Channels display zero; query/loading/error states are explicit and an unavailable query never displays fabricated zero data. Refresh after new committed messages and after the local-day boundary. Read-only statistics do not advance unread positions or wake Bots.
• Aggregate through the owning Channel read model and existing Host↔Client Bridge / API Gateway. Do not scan full histories or add a second message/activity store or schema migration.
• Use native DSH tokens/primitives and the existing compact Profile chart patterns. Keep chart rendering manageable for many Channels; provide a way to view the remaining rows instead of silently omitting totals.
• Real DSH light/dark and narrow Before/After screenshots plus E2E verifying totals, expansion and Channel navigation. Each issue has its own PR; pause for Human QA after this slice.

Test seams

Use the existing real Channel / Host query and Bridge / rendered Overview boundaries. Cover multiple Bot Admissions, mixed senders, paging-sized input, day boundaries, current Human nickname, missing/deleted/inaccessible Channels, late committed messages and restart. Assert visible counts and preserved canonical unread/attention facts rather than SQL statement shape or component internals.

Out of scope

Token or cost attribution, seven-day usage/Memory charts, Channel-level token allocation, external account linking, new wake rules and new Inbox categories. These remain separate Overview follow-on slices.