Initial import: chezmoi source for Omarchy (Hyprland)

Imported from prdlk/dotfiles master (efdd827), which supersedes the omarchy
branch (3031416). Drops the Umbriel, Noctalia, niri, CachyOS, macOS, and Blume
docs-site layers; docs/ is plain Markdown.

.chezmoiexternals/herdr.toml

@@ -0,0 +1,6 @@
+[".config/herdr"]
+    type = "git-repo"
+    url = "https://github.com/prdlk/herdr.git"
+    refreshPeriod = "168h"
+    [".config/herdr".pull]
+        args = ["--ff-only"]