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/README.md

@@ -82,7 +82,7 @@ node --test packages/control-board/tests/
 
 ```
 <dataRoot>/board/
-  index.json                       # summary: counts, waiting-on-you, seen, registered, registrationErrors, all records
+  index.json                       # summary: counts, waiting-on-you, seen, registered, registrationStale, registrationErrors, all records
   seen.json                        # Jason's "seen" marks (see below)
   sessions/
     <project>/
@@ -126,6 +126,13 @@ 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.
+A record is written before the launch script's own checks run, so a refused
+launch leaves a record whose pid is gone. The scan probes the recorded pid
+on every pass; when it is gone the record is stale: the row keeps the
+Registered line (marked stale, `registered.alive` false) but the derived
+task, project and workspace win and the sources say so. Stale rows are
+listed under `registrationStale` on the index. A record with no pid is
+never stale.
 
 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