Put the dual-bay sibling in the triage band, and fix the gage counterpart

The machine page opened with a dual-bay banner directly above a hero band saying
'Controlled by'. Both answer 'what am I looking at', so the sibling is now a chip
in the band. The band takes a generic extraitems prop rather than learning what
dualpath is - the pairing is resolved by the machines plugin, not from the
relationships endpoint.

MeasuringToolDetail filtered for a machine counterpart, but the import creates a
controls edge PC -> tool, so a gage's counterpart is a computer. It rendered
nothing on every metrology station that has a PC.

Verified on screen. Full suite 2178 passed, frontend 280 passed.

plugins/measuringtools/frontend/views/MeasuringToolDetail.vue

@@ -47,13 +47,20 @@
             </div>
           </div>
 
-          <!-- The 6am band. A gage usually has no controls edge at all,
-               and the band renders nothing when it has nothing to say - it is
-               here so the five asset pages stay one shape rather than five. -->
+          <!-- The 6am band: which PC drives this instrument.
+               A metrology tool is reached through the PC that runs it - the
+               import synthesizes one measuring-tool asset per metrology PC and
+               a 'controls' edge PC -> tool (stage_metrology), so the
+               counterpart here is a COMPUTER, exactly as on the machine page.
+               This was first written as counterparttype="machine" labelled
+               "Used on", which filtered for a counterpart that cannot exist
+               and so rendered nothing on every gage that had a PC. A hand-held
+               gage genuinely has no such edge, and the band correctly shows
+               nothing for it. -->
           <AssetTriageBand
             :assetid="tool.assetid"
-            counterparttype="machine"
-            counterpartlabel="Used on"
+            counterparttype="computer"
+            counterpartlabel="Controlled by"
           />
         </div>
       </div>