A confined engine.batch checked each step's file parameters before the batch
ran, but a step whose whole params was a `$N` reference became an earlier
step's result only at run time, so a file path in that result (for example a
manifest from essential.templateInfo) reached file.saveAs unchecked. Such
steps are now refused while file access is confined.
An image-sequence render writes numbered frame names that the check of its
output template never resolved, and each frame is created through any link
already at its name. A render output whose folder holds a link leading
outside the write roots (or one that cannot be resolved) is now refused when
it is queued and again when the queue renders.
Dylan M. Taylor
b4732955fc