R-366 slice 2 (decision 168): the host report carries the archives the restore-test skipped as another key's

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

internal/hub/report.go

@@ -129,6 +129,12 @@ type HostReport struct {
 	// wired; an empty `guests` list means the job runs and no guest has been trimmed yet. No secret.
 	GuestDiskTrim *GuestDiskTrimStatus `json:"guest_disk_trim,omitempty"`
 
+	// ForeignKeyArchives (R-366 slice 2, `09` §3 decision 168): per backup tier, the whole-guest archives the
+	// restore-test SKIPPED because they were written with another key (an earlier install of this box). This box
+	// cannot open them; the hub turns a CHANGE of this list into one operator event. Absent = not evaluated yet since
+	// the agent started (the hub keeps its last state); `tiers: []` = evaluated, none found.
+	ForeignKeyArchives *ForeignKeyArchivesStanza `json:"foreign_key_archives,omitempty"`
+
 	// LogTail is the agent's on-demand debug-ring tail (v0.83.0 observability) — the agent
 	// mirror of the controller's report log_tails channel. Present ONLY on the heartbeat
 	// right after the control envelope requested it (log_tail_requested); consume-once on
@@ -726,3 +732,18 @@ type WireRestoreDirective struct {
 	Archive string `json:"archive,omitempty"` // source archive/snapshot to restore from
 	VMID    int    `json:"vmid,omitempty"`
 }
+
+// ForeignKeyArchivesStanza wraps the per-tier list so "evaluated, none" (`tiers: []`) differs from "not evaluated"
+// (the stanza absent) without a null on the wire.
+type ForeignKeyArchivesStanza struct {
+	Tiers []ForeignKeyArchives `json:"tiers"`
+}
+
+// ForeignKeyArchives is one tier's count of archives written with another key (R-366 slice 2): the count and the
+// newest/oldest archive time (RFC3339, UTC). No key material — the fingerprints stay on the box.
+type ForeignKeyArchives struct {
+	Target string `json:"target"`
+	Count  int    `json:"count"`
+	Oldest string `json:"oldest"`
+	Newest string `json:"newest"`
+}