It had no production sender: every driver data change is already a
batch, and the comms-loss fan was converted earlier. DependencyMuxActor
drops its per-value receive, DriverInstanceActor drops the record, and
DependencyMuxActorTests' 13 sends move to the ValuePublishes.Single
one-item batch (same semantics through the batch path). XML docs and
the living docs (DriverLifecycle, VirtualTags, ScriptEditor) are
reworded; historical plan docs are left as written.
Refs #731#734
Claude-Session: https://claude.ai/code/session_01Ub9hGmYLQvn9XETzw7CMsT
Joseph Doherty
6636de1199