hst/enablement: move bits from system

This is part of the hst API, should not be in the implementation package.

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

system/link.go

@@ -2,24 +2,26 @@ package system
 
 import (
 	"fmt"
+
+	"hakurei.app/hst"
 )
 
 // Link calls LinkFileType with the [Process] criteria.
 func (sys *I) Link(oldname, newname string) *I { return sys.LinkFileType(Process, oldname, newname) }
 
 // LinkFileType maintains a hardlink until its [Enablement] is no longer satisfied.
-func (sys *I) LinkFileType(et Enablement, oldname, newname string) *I {
+func (sys *I) LinkFileType(et hst.Enablement, oldname, newname string) *I {
 	sys.ops = append(sys.ops, &hardlinkOp{et, newname, oldname})
 	return sys
 }
 
 // hardlinkOp implements [I.LinkFileType].
 type hardlinkOp struct {
-	et       Enablement
+	et       hst.Enablement
 	dst, src string
 }
 
-func (l *hardlinkOp) Type() Enablement { return l.et }
+func (l *hardlinkOp) Type() hst.Enablement { return l.et }
 
 func (l *hardlinkOp) apply(sys *I) error {
 	sys.msg.Verbose("linking", l)