Part markers become their own assets under the operation they serve

CHANGELOG.md

@@ -83,6 +83,20 @@ ADR-007 and ADR-002.
   `computers_machinelink_alerts` setting that ships OFF: a site may legitimately
   run several PCs on one machine number, and there the alerts fire on correct
   data. The collector response warns either way.
+- A part marker is its own asset. Several Telesis markers can serve one
+  operation number, so treating the operation as the marker collapsed separate
+  devices into one record: their configurations, which differ by COM port,
+  overwrote each other in the backup history, and no question about an
+  individual marker - how many there are, which port one is on, which one
+  failed - could be asked at all. There is one marker per PC, so the collector
+  now mints a Part Marker machine asset for a marker PC the same way it already
+  mints a CMM or a Keyence unit for a metrology PC: the PC `controls` the
+  marker, and the marker is `partof` the operation it serves. Because `controls`
+  propagates through `partof`, control of the operation still follows from
+  controlling its marker, and two markers on one operation no longer contest a
+  link only one of them can hold. Backups from a marker PC file against the
+  marker. Moving a marker to another operation archives the old membership
+  rather than deleting it.
 - Plugin contract 0.16.0: `get_settings_defaults()` lets a plugin declare the
   settings it owns (key, default, type, category, description, and whether an
   unauthenticated caller may read it). See `docs/PLUGIN-HOOKS.md`.