A LiveComponent that renders a completed conversation turn.

Displays the user message and assistant response for a single Omni.UI.Turn, with support for:

• Inline editing — the user can edit their message, which sends {Omni.UI, :edit_message, turn_id, Omni.Message.t()} to the parent LiveView to create a new conversation branch.
• Branch navigation — when a turn has multiple edits or regenerations, version navigation arrows are shown (delegated to version_nav in Omni.UI.CoreUI).
• Copy to clipboard — pushes an "omni:clipboard" event to the client with the text content for a given role.

Events

Events handled locally:

• "edit" — enters edit mode, populating the textarea with current text.
• "cancel" — exits edit mode.
• "change" — tracks textarea input.
• "copy" — pushes clipboard event to client.

Events forwarded to parent via send/2:

• "submit" — sends {Omni.UI, :edit_message, turn_id, message} to parent.

Events forwarded to parent via phx-click (no component handling):

• "omni:navigate" — branch navigation, handled by parent's handle_event.
• "omni:regenerate" — response regeneration, handled by parent's handle_event.