Judge a PC's backup by its stalest kind, not its newest

plugins/geenforce/api/routes.py

@@ -1079,10 +1079,52 @@ def _attach_backup_state(facts, hostnames):
     rows.sort(key=lambda revision: (revision.lastseenat is not None,
                                     revision.lastseenat or _EPOCH),
               reverse=True)
+
+    # Reduce to the FRESHEST revision per (host, kind), then judge a host by its
+    # STALEST kind.
+    #
+    # Until part markers, a PC reported exactly one kind and "newest wins" was
+    # the same thing as "the truth". A marker bay reports two - ntlars for the
+    # machine's DNC settings and partmarker for the controller's patterns - and
+    # newest-wins then means the daily ntlars post keeps the badge green while
+    # the marker backup has been failing for a month. The failure would show
+    # only on that marker's own asset page, which is not where anyone looks to
+    # find out that something stopped.
+    #
+    # So: a host is healthy when EVERYTHING it backs up is current, and the
+    # badge names the kind that is not. Freshest-per-kind first, because
+    # lastseenat only moves on the newest revision of a chain - an older
+    # revision of the same kind keeps its original value and would otherwise
+    # read as stale for ever.
+    #
+    # KNOWN CONSEQUENCE: a device retired from a PC leaves its last revision
+    # behind, so that host stays stale until the revision is pruned or removed.
+    # That is the honest failure direction - it complains about a backup that
+    # genuinely is not running any more, rather than staying quiet about one.
+    freshest = {}
     for revision in rows:
         key = (revision.sourcehostname or '').lower()
+        if key not in facts:
+            continue
+        kindkey = (key, revision.backupkind)
+        if kindkey not in freshest:
+            # rows are already newest-confirmed-first, so the first is freshest.
+            freshest[kindkey] = revision
+
+    stalest = {}
+    for (key, _kind), revision in freshest.items():
+        current = stalest.get(key)
+        if current is None:
+            stalest[key] = revision
+            continue
+        # None (never confirmed) is worse than any date.
+        if revision.lastseenat is None:
+            stalest[key] = revision
+        elif current.lastseenat is not None and revision.lastseenat < current.lastseenat:
+            stalest[key] = revision
+
+    for key, revision in stalest.items():
         entry = facts.get(key)
-        # First row per host wins.
         if entry and entry['backuplastseen'] is None:
             entry['backupkind'] = revision.backupkind
             entry['backuplastseen'] = (