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

docs/chezmoi/externals-and-ignore.mdx

@@ -60,6 +60,7 @@ Per-app config repos, one file each in `.chezmoiexternals/<app>.toml`. Each is a
 | `yazi.toml` | `~/.config/yazi` | [prdlk/yazi](https://github.com/prdlk/yazi) |
 | `kitty.toml` | `~/.config/kitty` | [prdlk/kitty](https://github.com/prdlk/kitty) |
 | `ghostty.toml` | `~/.config/ghostty` | [prdlk/ghostty](https://github.com/prdlk/ghostty) |
+| `herdr.toml` | `~/.config/herdr` | [prdlk/herdr](https://github.com/prdlk/herdr) — `plugins/github/` (runtime plugin checkouts) is gitignored there |
 | `omarchy.toml` | `~/.config/omarchy` | [prdlk/omarchy](https://github.com/prdlk/omarchy) — `shell.json`, hooks, menu extensions, themed templates; git-installed themes/plugins are gitignored there and restored by its `install-extras` script, `calendars.json` is never committed |
 | `noctalia.toml` | `~/.config/noctalia` | [prdlk/noctalia](https://github.com/prdlk/noctalia) — hand-written `config.toml` (shell, screenshot folder, theme, plugins, night light, notifications, OSD, wallpaper), `bar.toml` (bar layout, per-monitor overrides, widgets), and `palettes/` (custom palette JSON); merged under the GUI's unmanaged `~/.local/state/noctalia/settings.toml`, which wins on conflicts; `plugins/` holds runtime state with embedded tokens and is gitignored there. Linux desktop/laptop roles only ([role gate](#chezmoiignore)) |