CSyncManager extracts the headers-first IBD planner from main.cpp into
its own translation unit. main.cpp loses ~570 lines of file-scope state
and helper functions; the headers handler, block-delivery latency
tracking, stall-recovery, and per-peer Tick cadence now route through
g_syncManager.
MaybeMigrateLevelDbToRocksDb() is now reachable via -migratechaindb /
-migratechaindbforce in init.cpp. Reads from <datadir>/txleveldb and
writes byte-for-byte identical records into <datadir>/rocksdb via a
new CRocksTxDB::WriteRawRecordForMigration() shim over WriteRaw.
Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>
