WIP: judge an access by who writes it, and act on its path only on a warrant (issue 567)

Paused: ADR 0325 replaces runs-as and the group grant. Kept for reuse: the
bounded descriptor walks, the warrant-backed access act (share, create),
the access wait and the missing-path waiting state.

internal/link/queue.go

@@ -62,6 +62,10 @@ type Queue struct {
 	// JudgeDirectories judges this node's declared directories read-only, asked by the controller over the
 	// link (novox/hq issue 358). Nil answers every such ask with a refusal.
 	JudgeDirectories JudgeDirectoriesFunc
+	// AccessAct judges and runs an act on a read-write access's path — the share act, or making a missing
+	// path — asked by the controller on an approved warrant (novox/hq ADR 0322 §6, ADR 0324). Nil answers every
+	// such ask with a refusal.
+	AccessAct AccessActFunc
 	Say              Announce
 	Timeout          time.Duration