v0.5.0: slice 5 Phase B — the host-root surface (mounts + SMART + grow + destructive gate)

The privileged write surface, isolated behind a narrow, arg-validated, adversarially-
tested seam (HostOps), the same discipline as the slice-4 gate. Completes slice 5.

- internal/storage: HostOps seam + SudoHostOps (systemd .mount units by fs-UUID, detach,
  SMART, lvs) via sudoers allowlist + fixed arg vectors, no shell; NoopHostOps fallback.
- validate.go: strict UUID/mount-path/device/LVM validators + in-process systemd-escape.
  Headline test: adversarial matrix (metacharacters/traversal/malformed) refused with
  zero exec.
- smart.go: smartctl SATA + NVMe parse, UNKNOWN-degrade; lvs thin-pool metadata fill.
- observer enrichment (Observe only): fills smart + thin-pool metadata.
- watchdog: benign re-mount response off the poll path (DevicePresent probe, rate-limited).
- reconcile: ActionResize (benign, grow-only) + proxmox.ResizeLXC; destructive storage ops
  (ClassStorageWipe/Decommission) through the slice-4 gate, target-scoped; built+tested,
  inert live.
- --selftest=storage [-watch] live harness; configs/felhom-agent.sudoers; privileged.* knobs.

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

internal/reconcile/classify.go

@@ -17,6 +17,11 @@ const (
 	ClassStart     OpClass = "start"
 	ClassStop      OpClass = "stop"
 	ClassSetConfig OpClass = "set_config" // benign sizing/description changes only
+	ClassResize    OpClass = "resize"     // GROW-only rootfs/volume resize (slice 5 Phase B)
+
+	// Benign storage attach — re-mount-by-UUID of a known target whose device returned
+	// (slice 5 Phase B). Additive (no data loss), so benign by construction.
+	ClassStorageMount OpClass = "storage_mount"
 
 	// Benign by construction — classified now, executors land in later slices.
 	ClassCreate  OpClass = "create"  // provision a NEW guest (restore-to-new, slice 7)
@@ -76,7 +81,7 @@ func (p Provenance) internalEvidence() bool {
 //   - an UNKNOWN class fails safe → Destructive (require a signature).
 func Classify(class OpClass, prov Provenance) Disposition {
 	switch class {
-	case ClassStart, ClassStop, ClassSetConfig, ClassCreate, ClassRestart:
+	case ClassStart, ClassStop, ClassSetConfig, ClassResize, ClassStorageMount, ClassCreate, ClassRestart:
 		return Benign
 	case ClassGuestDestroy, ClassStorageWipe, ClassRestoreOverwrite, ClassDecommission:
 		if prov.internalEvidence() {
@@ -100,6 +105,8 @@ func classOfAction(k ActionKind) OpClass {
 		return ClassStop
 	case ActionSetConfig:
 		return ClassSetConfig
+	case ActionResize:
+		return ClassResize
 	default:
 		return OpClass(k)
 	}