Stage 4 of the realism migration. Lifts the driver Protocol into a
proper ABC with default plant_file/read_file methods (raise
NotImplementedError), and adds get_driver_for(action) so the
orchestrator worker can dispatch by action shape without isinstance
chains.
SSHDriver now inherits ActivityDriver and implements:
- plant_file: streams base64 via stdin (ARG_MAX-safe, mirrors
decnet.canary.planter; commit c17b9e0). Honours mtime via touch -d
so realism-planned files don't all stamp at wall-clock-now.
- read_file: docker exec cat with FileNotFoundError on rc=1, used by
the upcoming EditAction (stage 3b).
EmailDriver inherits ActivityDriver. Driver alias kept for back-compat
during the migration; removed once realism stages 5-7 land.
anti
636c057cc5