fix(diagnostics): close route recovery gaps

[rldyourmnd]

Summary

• permit the queue-only route reconciler timer through the observer fixed service inventory
• retry remote HEAD across multiple bounded rounds so a full one-minute route convergence stays within one exporter generation
• retain rejection of unrelated systemd units and preserve the existing ten-minute run budget

Verification

• make verify
• git diff --check
• tests prove three transient HEAD failures recover with zero failed generation