Changes made for Pathfinder 5226 controllers.

Traversing-task handshake: before writing START_MDI the driver now walks reject (bit 4 low), release (bit 4 high, bit 6 low), then activate, one produced frame per step, to avoid drive alarm A07487.

Keepalive moved from a 100-frame counter to a 2 s wall-clock interval, and it is skipped while an explicit message is in flight so keepalive reads cannot flood the drive.

All temporary bench printf diagnostics removed from both files. The "complete the explicit message even on error" fix stays.