add a README.md for nova (#3066)

also remove some old inputs files

Author: zingale

Exec/science/nova/README.md

@@ -0,0 +1,16 @@
+# `nova`
+
+This sets up a classical nova envelope on the surface of a carbon/oxygen
+white dwarf using initial models provided by Ami Glasner.
+
+It is recommended to begin with the `inputs_nova_t7` inputs file.
+
+
+## Publications
+
+This problem setup was used in:
+
+* *Multidimensional Nova Simulations with an Extended Buffer and Lower
+  Initial Mixing Temperatures*, A. Smith Clark & M. Zingale, 2025,
+  Open Journal of Astrophysics, volume 8,
+  https://doi.org/10.33232/001c.136890