Add herdr config.

home-modules/herdr.nix

@@ -0,0 +1,41 @@
+{ ... }: {
+
+  home.file.".config/herdr/config.toml" = {
+    text = ''
+      [keys]
+      prefix = "ctrl+a"
+
+      # Use tmux-style session selection for workspace navigation.
+      workspace_picker = "prefix+s"
+      settings = "prefix+shift+s"
+
+      # Side-by-side panes (tmux's "|" / "\" split -h).
+      # NOTE: "backslash" as a key name is inferred, not confirmed in the docs.
+      # Verify against `herdr --default-config` and adjust if it doesn't bind.
+      split_vertical = "prefix+backslash"
+
+      # Stacked panes (tmux's "-" / "_" split -v).
+      split_horizontal = "prefix+minus"
+
+      detach = "prefix+d"
+
+      # Kept "f" for next-tab like the old tmux config; herdr's
+      # previous_tab default (prefix+p) already matched.
+      next_tab = "prefix+f"
+
+      close_pane = "prefix+w"
+      close_tab = "prefix+shift+w"
+
+      # Kept "," for rename-tab like the old tmux default.
+      rename_tab = "prefix+,"
+
+      [ui]
+      mouse_capture = true
+
+      [session]
+      # Replaces tmux-resurrect/continuum: agents and panes come back on reattach.
+      resume_agents_on_restore = true
+    '';
+  };
+
+}