Remove obsolete sol sync command
Sync is being replaced by `sol transfer send` (separate work). This removes
the sync module, its tests, all CLI wiring, and the supervisor integration.
The `--remote` flag and remote-mode infrastructure are preserved for reuse.
Deleted:
- observe/sync.py (SyncService, RemoteClient, check_remote_health)
- tests/test_sync.py
- apps/observer/tests/test_client.py
Edited:
- sol.py: removed sync from COMMANDS and GROUPS
- think/supervisor.py: removed import, start_sync(), and remote-mode sync launch
- tests/test_supervisor.py: removed test_start_sync
- docs/SOLCLI.md: removed sync from command table