Add mosaic launch <seat> with seat registration for the control board (#1504)

New package packages/seat and wrapper scripts/mosaic. `launch <seat>` writes
<dataRoot>/seats/<layout>/<seat>/registration.json and then execs the seat's
launch.sh unchanged; `seat task <seat> <text>` edits the task only. The board
reads registrations, matches by sessions directory, and lets a registered
task, project or workspace override the derived value with a source tag.
The four repository launch scripts register themselves unless already
registered or run with --check. Fleet launchers untouched; one-liner on the
plan page.

Review found the record path keyed by seat name alone (repo and fleet
"darkwing" would collide); fixed by keying on layout. Also: the Pi pin
refusal now names installed and required versions.

Tests: seat 15, control-board 89, launch scripts 5, registry 69, config 24.

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

packages/control-board/README.md

@@ -82,7 +82,7 @@ node --test packages/control-board/tests/
 
 ```
 <dataRoot>/board/
-  index.json                       # summary: counts, waiting-on-you list, seen list, all records
+  index.json                       # summary: counts, waiting-on-you, seen, registered, registrationErrors, all records
   seen.json                        # Jason's "seen" marks (see below)
   sessions/
     <project>/
@@ -95,8 +95,9 @@ only when Jason clicks "Seen" or "Unsee" on the page (via `POST
 the agent's newest message still has that exact `lastActivity` timestamp —
 as soon as the agent writes anything new, `lastActivity` changes, the mark
 no longer matches, and the row falls back into "Waiting on you" on its own.
-Every row also shows three "what and where" fields, each derived from the
-session log and tmux or shown as the word "unknown", never guessed:
+Every row also shows three "what and where" fields, each taken from the
+seat's registration when it has one, else derived from the session log and
+tmux, else shown as the word "unknown", never guessed:
 
 - **Task** — the session's first user message (collapsed to one line, 240
   characters). pi logs carry no task envelope, so this is the only
@@ -112,6 +113,20 @@ session log and tmux or 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`).
 
+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
+those and matches a record to a row by its sessions directory, never by
+name alone. A registered task, project or workspace replaces the derived
+value and the row's source field (`taskSource`, `activeProjectSource`,
+`workspaceSource`) reads `registration`; the page shows a small source tag
+next to the value and a "Registered" line in the detail with the start time,
+harness, pid and tmux session. An empty task or a null project or workspace
+in the record leaves the derived value in place. Rows with no registration
+are exactly as before. The board only reads `seats/`; `mosaic launch` and
+`mosaic seat task` are the only writers. A malformed record is listed in
+`registrationErrors` on the index (and on stderr for `scan`) and skipped.
+
 Marked rows are listed under a collapsed "Seen (N)" section on the page,
 each with an "Unsee" button, so nothing marked is ever out of reach. Each
 project table has "Hide offline" and "Hide seen" checkboxes (both on by
@@ -140,6 +155,8 @@ values), the scan refuses rather than silently dropping every mark.
   "workspace": "/mnt/storage/src/mosaic-stack",
   "workspaceSource": "tmux-pane",
   "activeProject": "mosaic-stack",
+  "activeProjectSource": "workspace-git-root",
+  "registered": null,
   "lastActivity": "2026-09-12T15:04:33.000Z",
   "ageSeconds": 42,
   "lastAssistantText": "Ready for the next step whenever you are.",