feat(dashboard): LLM stats answer who/what spends tokens — member scope chips and spend breakdowns

The stats section was designed single-user: four global charts, no
attribution. Request metadata rows now carry the session's source and
the frame's agent_id/depth (additive ensure_column), denormalized at log
time by the LoggingModel from the owner's pool — off the turn's hot
path, degrading to NULLs, never to a lost row.

The dashboard gains member scope chips filtering every chart, and a
breakdown row splitting the range's billed tokens by member, kind
(chat / sub-agents / cron / system agents / channels), agent, model and
provider — a sub-agent's spend is attributed to the sub-agent itself.
Rows predating the columns group under 'older data'.

docs/index.md

@@ -12,7 +12,7 @@ This index will grow over time. Right now it covers the chat window, the inbox,
 | --- | --- |
 | [chat.md](chat.md) | The chat window: full-page vs docked, the tab bar and what lands where, the composer's controls, the slash commands, and what happens while an answer is being written |
 | [inbox.md](inbox.md) | The Inbox: the three kinds of pending request, why background work asks here rather than in the chat, answering one (and the time-limited approvals), and why an unanswered card means a stopped job |
-| [dashboard.md](dashboard.md) | The Dashboard: the instance status line, the LLM usage charts (everyone's together, counts never content), the pending-inbox section, and what the no-models banner means |
+| [dashboard.md](dashboard.md) | The Dashboard: the instance status line, the LLM usage charts (filterable per member, with spend broken down by member, kind, agent, model and provider — counts never content), the pending-inbox section, and what the no-models banner means |
 | [security-groups.md](security-groups.md) | Security groups: allow / ask / deny per tool, the shield in the chat, what the default group already permits, and how an admin edits the rules |
 | [memory.md](memory.md) | Private and shared memory: what goes where, the indexes and history log, why some shared facts can't be changed on request |
 | [agents.md](agents.md) | Agents: the three kinds (chat, task, system), which one you are talking to and why, the specialist agents the assistant delegates to, how the model is chosen, and adding a custom agent |