Open 2.3.1-dev

Post-release: bump the version suffix and open a changelog stub, so the next
change has somewhere to write its entry while the context is fresh.

Note for next time: the suffix is dropped *before* tagging and re-added here.
Doing only the second half published a `2.3.0.dev0` pre-release, which cost a
tag move to recover from. Checking `__version__` immediately before tagging is
the whole guard.

Co-Authored-By: Claude Opus 5 <noreply@anthropic.com>

Author: Technologicat

CHANGELOG.md

@@ -1,5 +1,12 @@
 # Changelog
 
+**2.3.1** (in progress):
+
+*No user-visible changes yet.*
+
+
+---
+
 **2.3.0** (14 August 2026) — *"Mind the gap"* edition:
 
 **New**:

unpythonic/__init__.py

@@ -7,7 +7,7 @@
 for a trip down the rabbit hole.
 """
 
-__version__ = '2.3.0'
+__version__ = '2.3.1-dev'
 
 from .amb import *  # noqa: F401, F403
 from .arity import *  # noqa: F401, F403