control board: show the model each seat is running (#1503)

Jason asked for the running model (sonnet, opus, gpt-6-astra) on the
board. readSession keeps model and provider from the log's latest
model_change entry or assistant turn, whichever is later, so a /model
switch shows on the next scan; scanAgent exposes both; the page shows the
model under the agent name with the provider in the hover and a Model
detail row. Blank when the log names none.

Live check on a scratch board against the real data root: all 42 rows
carried a model. Board 91/91. Sonnet review caught a double-escaped hover
title; fixed.

Co-Authored-By: Claude Fable 5.1 <[email protected]>

packages/control-board/README.md

@@ -113,6 +113,12 @@ tmux, else shown as the word "unknown", never guessed:
   tmux could not be asked, the `cwd` from the session log. The record says
   which one it used (`workspaceSource`: `tmux-pane` or `session-cwd`).
 
+- **Model** (under the agent name, and a detail row with the provider) —
+  the model the seat is running, from the log's latest `model_change` entry
+  or assistant turn, whichever is later, so a `/model` switch mid-session
+  shows up on the next scan. Blank until the log names one; a seat with no
+  pi log (rocko) has none.
+
 A seat started through `scripts/mosaic launch <seat>` (see
 `packages/seat/README.md`, #1504) has a registration at
 `<dataRoot>/seats/<layout>/<seat>/registration.json`. The scan reads every one of
@@ -166,6 +172,8 @@ values), the scan refuses rather than silently dropping every mark.
   "registered": null,
   "lastActivity": "2026-09-12T15:04:33.000Z",
   "ageSeconds": 42,
+  "model": "gpt-6-astra",
+  "provider": "openai-codex",
   "lastAssistantText": "Ready for the next step whenever you are.",
   "lastError": null,
   "skippedLines": 0,