Gap 1: generalise Fleetd.LeadMailboxOpener (and FleetdRuntime's field) from the concrete
LeadMailbox to a new closeable LeadChannelHandle (LeadChannel + AutoCloseable), so a test can
fake the configured-coordinator path without a real broker. FleetdAssemblyCoordinatorLifecycleTest
drives FleetdAssembly.assembleAndStart with a coordinator: block and a fake channel, proving the
assembly builds it and shutdown closes it.
Gap 2: move reportRoleFallbackGaps(cfg) and assertChartersNameOnlyRegisteredTools(cfg) out of
Fleetd.main and into FleetdAssembly.assembleAndStart, immediately after cfg.validateAll(), so
both run inside the tested assembly boundary before any I/O. FleetdAssemblyRoleFallbackBoundaryTest
pins the moved call site behaviourally (captured log output), not by reading source text.
Both new tests were verified red under a targeted mutation (a non-closing/null coordinator for
gap 1; deleting the moved call for gap 2) and restored.
Dai Ha