release v2.3.1

Patch release: ticket/decision sidebars load on first open (T-352), plus
the KWin frameless-chrome map fix (T-351) and the transient pql-failure
retry (T-350) that landed since 2.3.0.

Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>

pubspec.yaml

@@ -13,7 +13,7 @@ description: >-
   subsystem handlers (pane, files, editor, git, pql), and the
   extension framework.
 publish_to: none
-version: 2.3.0
+version: 2.3.1
 repository: https://github.com/postmeridiem/clide
 # Short user-facing tagline (the welcome subtitle, web meta
 # description, etc.). Baked into lib/src/build_info.g.dart by