dsh-plugin-edit-regenerate: Modify user messages in history and regenerate

dsh-plugin-edit-regenerate is a DSH plugin designed to address the requirement of correcting sent user prompts within a session. It enables users to edit historical messages and regenerate responses based on the modified content without creating a new session. The plugin utilizes a fork mechanism to ensure the original session remains unchanged; modifications to non-initial messages fork out a new sub-session, while modifications to the initial message create a new session. Core functions include providing a "✎ Edit" option under user messages, preserving the original "⧉ Copy" action, and registering a Cordis service. Please note that attachments are discarded after editing and are only resent as plain text. For installation, select the appropriate profile based on the DSH Desktop or Web environment, and install via command line or by manually configuring dependencies. Restart DSH after installation or update.