Brings windows-support up to date with main (T-404/405/406, T-413–416, T-421, the T-422 workspace-lifecycle epic, and the 2.4.0 release). Conflict resolutions: - terminal_pane.dart: keep the Windows PowerShell shell selection and main's workspace-cwd fix (T-381) together. - tool_check.dart: accept main's deletion (dead, unreferenced code). - CHANGELOG.md: keep both Unreleased sections. Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>