herdr: move config to prdlk/herdr external; document OSC 8 links

docs/terminal/ghostty.mdx

@@ -31,6 +31,7 @@ It is the default everywhere a desktop picks a terminal: `$TERMINAL` in the [Umb
 | `mouse-hide-while-typing` | `true` |
 | `copy-on-select` | `false` |
 | `confirm-close-surface` | `false` |
+| `link-url` / `link-previews` | `true` / `true`. Under tmux (`mouse on`) tmux receives the click, so open links with `ctrl+shift+click`; tmux opens OSC 8 links on a plain `ctrl+click` |
 | `app-notifications` | `no-clipboard-copy,no-config-reload` |
 | `quit-after-last-window-closed` | `false`, delay `5m` |
 | `command` | `shell:$HOME/.local/bin/ghostty-tmux` (see [Sessions](#sessions)) |