Audit Legacy instability and allow unstable supported writing

Persist repaired Age writing and provisional instability penalties, retain fatal diagnostics for unsupported content, and hide TerraBlender's deferred placeholder biome from creative and JEI.

gradle.properties

@@ -36,7 +36,7 @@ mod_name=Rivencraft
 # The license of the mod. Review your options at https://choosealicense.com/. All Rights Reserved is the default.
 mod_license=LGPL-3.0-or-later
 # The mod version. Rivencraft uses the x.y.z.b policy documented in README.md.
-mod_version=0.5.0.0
+mod_version=0.5.1.1
 immersive_portals_version=6.0.7
 terrablender_version=4.1.0.8
 serene_seasons_version_id=B6nTjh4b