control board: reply from the board through agent-send.sh (#1505)

Piece 2 of the MVP (#1503). A one-line reply box and Send in the detail
of rows with a live registration; POST /api/reply runs
tools/tmux/agent-send.sh -s <session> -S <host>:control-board
[-L <socket>] -m <text> once for one seat and returns the exit code,
stdout and stderr. The page shows delivered or failed with the tool's
stderr; other rows say "reply needs a registered seat". No send-keys,
queue, retries, history or broadcast; packages/seat and agent-send.sh
untouched. Every message ends with a fixed trailer telling the seat to
answer in its own session (Jason's refinement after the first Gate C
exchange; the board has no pane). Board suite 98/98.

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

docs/SESSIONS.md

@@ -223,3 +223,4 @@ are never rewritten or removed; corrections are new entries.
 - 2026-09-12 — darkwing (Claude Code, coordinator; formerly jarvis) — Seat registration (#1504), Jason's go on the professor session's brief: new `packages/seat` and `scripts/mosaic` (`launch <seat>` registers then execs the launch script unchanged; `seat task` edits the task); board reads `<dataRoot>/seats/<layout>/<seat>/registration.json` and lets registered task/project/workspace override derived values with a source tag; the four repo launch scripts register themselves; fleet one-liner written for orch-01. Tests: seat 15, board 79 → 89, launch scripts 5, registry 69, config 24. Sonnet review found a seat-name collision across layouts; fixed by keying on layout, second pass APPROVED. Live check on a scratch server against a temp data root. Also found Jason's launch refused on the Pi pin (node_modules 0.84.4 vs pin 0.85.1 since 557aba0f); `npm ci` fixed it, the refusal now names both versions; the pin stays unless Jason decides otherwise.
 - 2026-09-12 — darkwing (Claude Code, coordinator) — #1504 follow-up on two defects the professor session reported and this session verified: the darkwing launch test leaked fixture registrations into the real data root (flock spawn without the fixture config; fixed and guarded so a leak fails), and a refused launch left a dead-pid record the board honoured (scanner now probes the pid; stale records are shown but do not override). Fleet launchers marked not planned per Jason. Board 90/90, seat 15/15, launch scripts 5/5. Committed and pushed to refactor.
 - 2026-09-12 — darkwing (Claude Code, coordinator) — Control board: model per row (#1503) on Jason's ask: readSession tracks model/provider from the latest model_change entry or assistant turn; page shows the model under the agent name and a Model detail row. Live check on a scratch board: all 42 real rows named a model. Board 91/91. Committed and pushed to refactor.
+- 2026-09-12 — darkwing (Claude Code, coordinator) — Control board piece 2, reply-from-board (#1505, brief by Jason): `POST /api/reply` runs `tools/tmux/agent-send.sh` for one registered, live seat and returns the exit code and streams; the page has a reply box in registered live rows' detail with delivered/failed receipts. Live check on a scratch tmux session through the real agent-send.sh: delivered, then a failure receipt with the tool's stderr. Board 98/98. Gate C first exchange ("pizza?") delivered and read back within one scan; the seat's send-back to control-board was refused as expected, so every board message now ends with a fixed trailer (Jason's ruling via the professor session). Committed and pushed to refactor.