Caught before deploy by tracing a.Path back to its source, not by a failure. The
0.184.0 image is superseded and must not be shipped.
ReconcileDriveGates resolves the target as isTarget[a.Path], and a.Path is the
REGISTERED StoragePath -- for an external drive that is the GUEST path
/mnt/felhom-drives/<name>, not the agent's host MountPath (/mnt/<name>) that
/disks reports. driveTargetByPath keyed on MountPath alone, so the lookup never
matched: every absent drive, the target included, fell through to the generic
storage_disconnected.
The alarm would have looked wired, passed its own unit tests, shipped, and been
silently wrong on exactly the drive it exists for -- the same defect class E-2b
was opened to fix, one level down.
Now keyed under BOTH paths, mirroring planDriveGates which already registers
present[] under GuestPath and MountPath for the same reason.
Red-proof: MountPath-only keying fails with "the backup target is not resolvable
by its GUEST path -- the gate passes a.Path (the registered StoragePath), so the
backup-target branch would never fire".
Green gate: build + vet + test rc=0, run separately from this commit.
