Release 4.0.0

Bump vsn to 4.0.0 and date the CHANGELOG entry. Major release: callback
results returning an Erlang string now arrive in Python as a list of
integers, matching call arguments, and nothing raises on upgrade.

Author: benoitc

CHANGELOG.md

@@ -1,6 +1,15 @@
 # Changelog
 
-## Unreleased
+## 4.0.0 (2026-08-15)
+
+### Breaking Changes
+
+- **Callback results returning an Erlang string** - a string returned from an
+  Erlang callback (`"abc"`, a list of integers) now reaches Python as
+  `[97, 98, 99]` rather than `'abc'`, the same conversion call arguments have
+  always used. Return a binary (`<<"abc">>`) for a Python `str`. Nothing raises
+  on upgrade, so check what your registered callbacks return before deploying.
+  See the encoding change under Changed below.
 
 ### Added
 

src/erlang_python.app.src

@@ -1,6 +1,6 @@
 {application, erlang_python, [
     {description, "Execute Python applications from Erlang using dirty NIFs"},
-    {vsn, "3.1.1"},
+    {vsn, "4.0.0"},
     {registered, []},
     {mod, {erlang_python_app, []}},
     {applications, [