fix: drive storage cleanup through reset before discovery (#5555701)

[williampnvidia]

Summary

• Stop Scout's discovery/no-API path from performing hidden NVMe/HDD/SAS cleanup;
  discovery now leaves destructive storage cleanup to the API-directed reset path
• Add cleanup context to WaitingForCleanup so the state machine can distinguish
  initial discovery cleanup from deprovision cleanup and route recovery correctly
• Drive initial discovery through WaitingForCleanup { InitialDiscovery } before
  returning Scout Action::Discovery
• Preserve HostInit cleanup context across repeated NVMECleanFailed retries so a
  successful retry returns to HostInit/WaitingForDiscovery, not the deprovision flow
• Add regressions covering firmware-upgrade Scout boots, assigned discovery-image
  boots, and repeated HostInit cleanup failures

Recovery context note

NVMECleanFailed recovery currently uses FailureSource::StateMachineArea(HostInit)
to remember that the failure happened during initial discovery cleanup. That keeps
this fix scoped and avoids changing serialized FailureCause shape in this PR.
A follow-up should consider storing cleanup context directly on the storage-cleanup
failure cause instead of inferring it from FailureSource.

Dev environment validation

• Deployed the local Carbide build into local-dev control-plane
  environment and verified the updated pods rolled out
• Normal delete path: provisioned a host, deleted it, observed API cleanup
  state, Scout RESET, NVMe cleanup, successful cleanup_machine_completed,
  and no destructive cleanup during the later DISCOVERY
• Force-delete/re-ingest path: force-deleted the host, observed the predicted
  host move through WaitingForCleanup { InitialDiscovery }, the actual host
  receive RESET, cleanup complete successfully, then DISCOVERY log the
  no-API cleanup skip message
• Injected an NVMe cleanup failure in Scout for the delete path and verified
  the machine moved to NVMECleanFailed
• Restored the non-failing Scout artifact, rebooted the host, and verified the
  machine recovered from NVMECleanFailed
• Repeated the injected NVMe cleanup failure and recovery validation for the
  force-delete/re-ingest path
• Verified API state transitions and Scout cleanup behavior in Loki logs

Test plan

• cargo +1.90.0 fmt --all
• git diff --check