v0.22.0: expose durable_id in GET /disks (enables controller guided storage)

localapi.DiskInfo gains durable_id (from StorageTarget.DurableID, "uuid:<fs-uuid>"
for usb/local-dir). The de-privileged controller can't read a device's fs UUID
but assign mounts strictly by UUID — this read-only field is the only way it
learns the assign key. No new privilege, no gate change.

Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>

cmd/felhom-agent/main.go

@@ -43,7 +43,7 @@ import (
 
 // version is the agent version. Overridable at build time with
 // -ldflags "-X main.version=<v>"; defaults to the in-repo CHANGELOG version.
-var version = "0.21.0"
+var version = "0.22.0"
 
 func main() {
 	var (