container: improve documentation

This change removes inconsistencies collected over time in this package.

Signed-off-by: Ophestra <cat@gensokyo.uk>

container/initproc.go

@@ -10,7 +10,7 @@ import (
 
 func init() { gob.Register(new(MountProcOp)) }
 
-// Proc appends an [Op] that mounts a private instance of proc.
+// Proc is a helper for appending [MountProcOp] to [Ops].
 func (f *Ops) Proc(target *check.Absolute) *Ops {
 	*f = append(*f, &MountProcOp{target})
 	return f