agent: a guest outside the agent's ACL is not a known guest (R-689, v0.136.0 regression)

PVE answers 403 permission denied, not "does not exist", for a vmid outside the felhom pool;
v0.136.0 turned that into a lookup failure and the local tier read UNKNOWN every evaluation
(measured on demo-hp). Such an archive is skipped. Red-proofed; verified read-only on demo-hp
with the pre-release binary.

Co-Authored-By: Claude Opus 5.5 (1M context) <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_0159rPz1ZhFKsS53msqPYxtS

internal/backup/r689_golden_test.go

@@ -91,3 +91,22 @@ func TestR689_AGuestLookupFailureIsUnknownNotEmpty(t *testing.T) {
 		t.Fatal("a failed guest lookup read as a clean answer")
 	}
 }
+
+// v0.137.0 — THE MEASURED ANSWER: the agent's token sees only its pool, so for the deleted guest PVE says 403
+// "permission denied at /vms/9100", not "does not exist" (demo-hp, right after v0.136.0 — the local tier read
+// UNKNOWN). Such a guest is not one this agent manages: its archive is skipped, the tier is not an error.
+//
+// COMPANION RED-PROOF (REPORT.md): drop the "permission denied" case — the pick errors.
+func TestR689_AGuestOutsideTheAgentsACLIsNotAKnownGuest(t *testing.T) {
+	const day = int64(86400)
+	now := int64(1790476000)
+	api := &fakeBackupAPI{aclGuests: map[int]bool{9100: true}, content: []proxmox.StorageContent{
+		{VolID: "local:backup/vzdump-lxc-9100-2026_08_21-17_59_15.tar.zst", Content: "backup", VMID: 9100, Size: 656970239, CTime: now - 37*day},
+		{VolID: "local:backup/vzdump-lxc-9201-2026_09_27-04_35_47.tar.zst", Content: "backup", VMID: 9201, Size: 8 << 30, CTime: now - 7*3600},
+	}}
+	r := NewBackupRunner(api, "local", proxmox.ModeSnapshot, "", "keep-last=1", quiet())
+	got, _, err := r.PickSettledRestoreCandidateOn(context.Background(), "local", time.Unix(now-day, 0).UTC())
+	if err != nil || got != "" {
+		t.Fatalf("picked %q err=%v — want nothing and no error (the only settled archive is not ours)", got, err)
+	}
+}