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/src/serve.mjs

@@ -67,7 +67,7 @@ export function loadPage(path = join(import.meta.dirname, "page.html")) {
 }
 
 // specs: agent specs to scan on each request. boardDir: where scan writes.
-export function createServer({ specs, boardDir, isAlive, now, page = loadPage() }) {
+export function createServer({ specs, boardDir, isAlive, now, seatsDir = null, page = loadPage() }) {
   return createHttpServer((req, res) => {
     const url = new URL(req.url, "http://localhost");
     if (req.method === "POST" && url.pathname === "/api/seen") {
@@ -79,7 +79,7 @@ export function createServer({ specs, boardDir, isAlive, now, page = loadPage()
             return sendJson(res, 400, { error: err.message });
           }
           try {
-            sendJson(res, 200, scan(specs, { boardDir, isAlive, now }));
+            sendJson(res, 200, scan(specs, { boardDir, isAlive, now, seatsDir }));
           } catch (err) {
             sendJson(res, 500, { error: err.message });
           }
@@ -97,7 +97,7 @@ export function createServer({ specs, boardDir, isAlive, now, page = loadPage()
     if (url.pathname === "/api/board") {
       let index;
       try {
-        index = scan(specs, { boardDir, isAlive, now });
+        index = scan(specs, { boardDir, isAlive, now, seatsDir });
       } catch (err) {
         res.writeHead(500, { "content-type": "application/json", "cache-control": "no-store" });
         return res.end(JSON.stringify({ error: err.message }) + "\n");