Add changelog entries for 0.40

Author: scottstanie

CHANGELOG.md

@@ -3,6 +3,19 @@
 All notable changes to this project will be documented in this file.
 The format is based on [Keep a Changelog](https://keepachangelog.com/en/1.0.0/).
 
+## [Unreleased](https://github.com/isce-framework/dolphin/compare/v0.40.0...HEAD)
+
+## [0.40.0](https://github.com/isce-framework/dolphin/compare/v0.39.0...v0.40.0) - 2025-06-
+
+### Fixed
+
+- Throw a better error for `dolphin` without any args
+
+### Changed
+
+- Remove `avg_coh` from optional phase linking outputs
+- `unwrap.py`: Combine sliding window mask with similarity mask for masking / interpolation
+
 ## [0.39.0](https://github.com/isce-framework/dolphin/compare/v0.38.0...v0.39.0) - 2025-06-09
 
 Largest visible change: Switch CLI to use `tyro` by @scottstanie in https://github.com/isce-framework/dolphin/pull/578