Add changelog fragment

Author: Jimbo4350

.changes/20260414_cardano_api_has_callstack.yml

@@ -0,0 +1,8 @@
+project: cardano-api
+pr: 1175
+kind:
+  - compatible
+description: |
+  Add HasCallStack constraints to standalone functions that call error
+  directly or indirectly, improving stack traces. Dijkstra-era placeholder
+  error messages are also improved.