proxmox: review fixes, real-host validation record, changelog

Phase 10. Two review passes (go-operator-reviewer, /code-review high)
over the branch, recorded in docs/reviews/2026-09-23-proxmox-provider-review/:
9 findings fixed, 3 accepted as documented limits, 7 rejected with a
reason.

- Delete removes the seed between the stop and the destroy, so a failed
  seed delete leaves the VM for the next Delete instead of leaking the
  ISO; a Permanent refusal on the every-node path fails the call.
- Create skips a probe VMID whose listed name is someone else's without
  waiting on its lock.
- The three answers Phase 0 never captured are fixtures now: a missing
  storage is a 400 (the Checker reports StorageNotFound), a hibernated
  VM is destroyable (Delete destroys ours), a paused VM stops.
- TestProxmox_lifecycle and TestProxmoxCheck_realHost passed on pv1-1
  (PVE 9.2.20); the docs record the run and drop "not yet run".

Co-Authored-By: Claude Opus 5.5 (1M context) <noreply@anthropic.com>

internal/provider/proxmox/check_test.go

@@ -230,7 +230,21 @@ func TestCheck_reasonsTable(t *testing.T) {
 				fx.fake.mu.Unlock()
 			},
 			wantReason:  reasonStorageNotFound,
-			wantMessage: "storage proxy-seeds on node pv1-1: fake: storage 'proxy-seeds' does not exist",
+			wantMessage: "storage proxy-seeds on node pv1-1: No such storage.",
+		},
+		{
+			// Not captured: a storage Proxmox knows but cannot use here.
+			name: "iso storage unusable on the node",
+			prep: func(fx *fixture) {
+				fx.fake.failWith("StorageStatus", fakeErr(500, "fake: storage 'proxy-seeds' is not online"))
+			},
+			wantReason:  reasonStorageNotFound,
+			wantMessage: "storage proxy-seeds on node pv1-1: fake: storage 'proxy-seeds' is not online",
+		},
+		{
+			name:       "another bad parameter is not a missing storage",
+			prep:       func(fx *fixture) { fx.fake.failWith("StorageStatus", loadAPIError(fx.t, "err_bad_param")) },
+			wantReason: provider.ReasonAPIError,
 		},
 		{
 			name:        "iso storage inactive",