Fix carrots on search.html

URLs should be listed in trees. The initial/head URL should be visible as the head with a carrot, and the following child URLs should be visible when the carrot is expanded.

Currently, the carrots are broken and the children are all expanded at once.

background.js gets the URL name from each tab visited.
The URL is saved in chrome.storage
Then foreground.js gets the URLs from chrome.storage and writes it to the search.html page, depending on which search is being accessed.

Start with search.html and foreground.js, then trace how foreground.js reads URLs from chrome.storage populated by background.js. Reproduce the page with multiple visited URLs and inspect the generated tree structure. Done means the initial URL appears as a head with a carrot and child URLs remain hidden until expanded.

Written by the indexing model from the issue text.