Require explicit manifest schemas

docs/troubleshooting.md

@@ -56,7 +56,8 @@ Symptom:
 
 Likely cause:
 
-- stale field name, typo, invalid enum, or invalid duration/path format.
+- stale field name, typo, invalid enum, invalid duration/path format, or an
+  unsupported local manifest schema/state marker.
 
 Diagnostics:
 
@@ -68,6 +69,10 @@ Safe fix:
 
 - align config with [Configuration](./config.md) and the
   [maintained examples](../examples/README.md).
+- for a manifest schema error, move the unsupported local state aside and
+  regenerate it; restore a verified current committed snapshot or republish
+  healthy regenerated state when appropriate. Do not add version or stage
+  markers by hand.
 
 Relevant reference: [Configuration](./config.md).