Cancel tab rename if I click elsewhere without editing the title

# Description of the new feature/enhancement

I sometimes accidentally double-click the title of a tab that I only intended to click once. Windows Terminal then opens the tab title for editing. When I see that the tab title got the focus, I instinctively click the session pane to move the focus back there. However, Windows Terminal interprets this click as meaning that I confirmed the rename. After that, the tab title no longer updates when the shell attempts to change it. To make it update again, I have to edit the title, delete all text, and confirm that.

I wish that Windows Terminal instead interpreted the click as meaning that I'm canceling the rename, if I have not edited the title.

# Proposed technical implementation details (optional)

Windows Terminal could either detect whether I edit the tab title at all while the edit box is open, or just compare the title to the existing one when the edit box loses the focus.

The Enter key should still confirm the rename even if the new title matches the current one.

Start by reproducing the tab-title rename flow: open a tab title for editing, click the session pane without changing the text, and observe the result. Locate the tab-title editing entry point and its focus-loss handling, then verify that an unchanged title is canceled while Enter still confirms it, including when the text matches the existing title.

Written by the indexing model from the issue text.