v4.0.6

pygls v2 compatibility fixes

• Fix window_show_message call signature: pygls v2 requires ShowMessageParams(type=..., message=...) instead of two positional arguments
• Fix @self.command handler signature: pygls v2 maps arguments to individual positional params, not a single ExecuteCommandParams object
• Add return after start_io() to prevent crash after LSP session ends
• Add LSP code action tests covering all synthesizers