Enable exact matching in zsh history search (Ctrl-R)

Searches like `^git checkout` aren't possible because fzf is matching on the first characters of the return of `fc -l 1` which are the commands id (e.g. `21453 git checkout why-is-this-branch-name-so-long`). Using `fc -ln 1` drops the number prefix and eliminates the need for `sed` here. Adding `-e` allows for extend matching (regex).