Shelve (15+ failures) now mimics manual stop/start behavior:
- Clears item.provider for fresh provider selection on retry
- Resets provider circuit breaker (providerFailures) for the old provider
- Reduces shelve duration from 5 min to 90s since the issue is stale
provider state, not a timing problem (manual restart works instantly)
Also adds comprehensive session-load logging:
- Logs package/item count on every session file read
- Logs errors when session file parsing fails (was silent before)
- Safety net: if primary session is empty but backup has packages,
automatically restores from backup
- Logs shutdown save with package/item counts
- Logs DownloadManager init state and cleanup policy
Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>
