segment-focused: Use reference as root seq

Motivated by errors with using the public builds as Nextclade datasets
via the "View in other platforms" feature.

<https://bedfordlab.slack.com/archives/C01G4B4UY31/p1763137307070419>

Author: joverlee521

segment-focused/config.yaml

@@ -132,7 +132,7 @@ refine:
 
 ancestral:
   inference: joint
-  root_seq: false
+  root_seq: config/{subtype}/reference_{subtype}_{segment}.gb
 
 traits:
   columns:
@@ -152,4 +152,4 @@ colors:
 
 export:
   title: false # use the title in the auspice JSON
-  # TODO - if we parameterise this here we can use the subtype wildcard to customise the title
+  # TODO - if we parameterise this here we can use the subtype wildcard to customise the title