release v2.3.0

Cut the accumulated Unreleased entries under a dated 2.3.0 heading and
bump pubspec + licenses self.version. Minor bump: the batch adds features
(file references, task dock, deny-simplify, ticket pick-up, type-filter
chips, VS Code/JetBrains keymaps) alongside the fixes.

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: 2.2.0
+version: 2.3.0
 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