quantumvm/vm.go: remove GetEngine() so the chain manager routes Q-Chain through
the linear consensuschain cert path (the same deterministic 2/3-stake BFT
certificate finality as C/D/P), not the undriven DAG engine. quantumvm already
implements the full chain.ChainVM/BlockBuilder surface; dropping GetEngine is the
whole change. Adds the _ chain.ChainVM + _ consensuschain.BlockBuilder asserts.
dexvm/factory.go: correct the stale 'Quasar consensus' comment — dexvm finalizes
via the linear cert path (Photon->Wave->Focus + 2/3-stake cert), same as C-Chain.