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/src/page.html

@@ -197,6 +197,7 @@
     if (reg.pid) parts.push("pid " + esc(reg.pid));
     if (reg.tmux && reg.tmux.session) parts.push("tmux " + esc(reg.tmux.session) + (reg.tmux.socket ? " (socket " + esc(reg.tmux.socket) + ")" : ""));
     if (reg.layout) parts.push(esc(reg.layout) + " layout");
+    if (reg.alive === false) parts.push("stale: pid " + esc(reg.pid) + " is gone, so the derived values are shown");
     return parts.join("; ");
   }