Formal A5d run on the merged branch surfaced a tier-detection probe
race: probePostgres (5s connect) failed against a HEALTHY postgres on
the same network (psql SELECT 1 from a peer container succeeds; the
wrapped cause is not surfaced by the bootstrap log). The compose is the
standalone tier BY DECLARATION (mode contract: mode chosen at install)
— pinning MOSAIC_STORAGE_TIER=standalone uses the documented env path
('storage tier=standalone source=process environment', observed in the
first scratch run) and removes the boot-order dependency on probe
timing entirely.
marcie