v0.4.0: slice 4 Phase B — reversibility gate + signed-op consuming layer

The security core of slice 4: hub-supplied intent is no longer trusted for
destructive change. The gate fronts the per-guest queue's executor, so every
mutation passes it. Reuses internal/authz for all crypto (surface untouched).

- Classifier (doc 03 §4): benign vs destructive by provenance + data-bearing-
  ness, NOT by verb. Destroy/overwrite of customer data is destructive unless
  agent-internal provenance (same-journaled-txn create, or agent-tagged scratch)
  makes it benign — and that provenance is journal-recorded, NEVER hub-sourced.
  Unknown op class fails safe to destructive.
- Reversibility gate: benign -> allowed unsigned; destructive -> requires a
  verified, role-scoped, action-bound operator signature, else pending_signature
  and never executed. Every decision audited (signal, never the guard).
- Signed-op consuming layer over authz.Verifier.Verify (locked pipeline
  untouched): role-scoping (doc 04 §4 — recovery=rotation only, operational=
  ordinary destructive + planned rotation) + op-to-action binding (op+host+
  guest+params must match the gated action).
- Signed-job orchestration: idempotency dedupe by nonce + journal-wrapped
  execution via an injected DestructiveExecutor (nil this slice — inert).
- Crash recovery (Note 1): Engine.Recover consumes the journal InFlight() set at
  startup (resume-or-rollback) — covers an op that crashed after the POST and
  before its terminal record, which idempotency dedupe alone cannot. Added
  TaskStatusOnce to the GuestAPI seam. Wired into daemon startup.
- Note 2: memory comparison canonicalized to MiB (desiredMemoryMiB) so a
  non-MiB-aligned MemoryBytes converges in one pass, not perpetual drift.
- Daemon: builds the verifier from config signers (none = nil verifier, the
  common slice-4 state), the gate (+SlogAudit), runs Recover before mutating.

Adversarial matrix proven against the REAL authz.Verifier with in-test-minted
SSHSIGs (framing replicated in reconcile's test binary; authz untouched, no
signing added to the verify-only package): unsigned job + unsigned desired-state
delta -> pending_signature; unknown signer/expired/replay-across-restart/wrong
host -> typed authz rejections; wrong guest/op/params -> binding_mismatch;
recovery key on ordinary destructive -> role_denied; hub-supplied scratch tag
ignored -> refused; valid+role+target+fresh nonce -> accepted then replay
rejected. Full module race-clean + vet-clean on the Linux build server.

Inert this slice: no destructive deltas served until slice 10; the destructive
path is classified, gated, and tested but not wired to live execution.

CHECKPOINT: Phase B complete (slice 4 done). Awaiting validation.

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

internal/reconcile/plan_test.go

@@ -73,6 +73,23 @@ func TestPlan_SpecDrift(t *testing.T) {
 	mustActions(t, got)
 }
 
+func TestPlan_MemoryNonAlignedConverges(t *testing.T) {
+	// Note-2 guard: a desired MemoryBytes that is NOT a clean MiB multiple must not
+	// cause perpetual drift. We compare in MiB and write the SAME MiB we compared, so it
+	// settles in one pass.
+	desiredBytes := int64(2049)*bytesPerMiB + 500000 // 2049 MiB + change → floors to 2049
+	d := desired(DesiredGuest{VMID: 100, Spec: &hub.GuestSpec{Cores: 2, MemoryBytes: desiredBytes}})
+
+	// First pass: actual is 2048 MiB → one SetConfig memory=2049.
+	got := Plan(d, actual(ActualGuest{VMID: 100, Run: RunStopped, SpecKnown: true, Cores: 2, MemoryMiB: 2048}), nil)
+	mustActions(t, got, Action{VMID: 100, Kind: ActionSetConfig, Params: map[string]string{"memory": "2049"}})
+
+	// Apply it: actual becomes 2049 MiB. Re-plan against the SAME desired → no action.
+	if got2 := Plan(d, actual(ActualGuest{VMID: 100, Run: RunStopped, SpecKnown: true, Cores: 2, MemoryMiB: 2049}), nil); len(got2) != 0 {
+		t.Fatalf("non-MiB-aligned memory did not converge (perpetual drift): %+v", got2)
+	}
+}
+
 func TestPlan_DiskNotReconciled(t *testing.T) {
 	// DiskBytes differs but is intentionally not reconciled (pct resize, later slice).
 	got := Plan(