control board: stale registrations and a launch-test leak (#1504)

Two defects in 69f99323, reported by the professor session and verified.

The darkwing launch test's flock-contention spawn ran without the fixture
config, so launch.sh re-entered scripts/mosaic against the real data root
and wrote fixture records for darkwing, dewey and filbert there. That
spawn now names the fixture config, and both launch test files set
MOSAIC_CONFIG to a nonexistent path and clear MOSAIC_LAUNCH_REGISTERED
process-wide, so a spawn that forgets fails instead of polluting.

A registration is written before the launch script's own checks, so a
refused launch left a record with a dead pid that the board honoured. The
scanner now probes the recorded pid (pidAlive, signal 0); a gone pid makes
the record stale: still on the Registered line with alive false, derived
task, project and workspace win, index gains registrationStale, CLI
summary gains a stale count.

Fleet launchers marked not planned per Jason. Board 90/90, seat 15/15,
launch scripts 5/5. Sonnet review APPROVED.

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

packages/control-board/tests/serve.test.mjs

@@ -567,7 +567,7 @@ test("CLI: scan --print marks a seen row with 's' and the summary line ends with
   const row = r.stdout.split("\n").find((l) => l.includes("agent1"));
   assert.ok(row, `expected an agent1 row in:\n${r.stdout}`);
   assert.equal(row[0], "s");
-  assert.match(r.stdout, /1 seen, 0 registered\)\s*$/m);
+  assert.match(r.stdout, /1 seen, 0 registered, 0 stale\)\s*$/m);
 });
 
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