Polish ringtail NixOS config and add documentation (#208)

## Summary
- Fix Super+Return keybinding to launch wezterm in sway
- Set fish as default login shell
- Remove `initialPassword` (real password already set)
- Add 1Password CLI + GUI, chezmoi, and dev tool packages (neovim, eza, fd, fzf, zoxide, starship, atuin, bat, ripgrep)
- Add ringtail reference card, update host inventory and reference index
- Changelog fragment

## Post-merge deployment
- `mise run provision-ringtail` to rebuild NixOS
- On ringtail: launch 1Password GUI, enable CLI integration (Settings > Developer > CLI integration)
- Chezmoi needs `.chezmoiignore` updates in the dotfiles repo (separate task)

Reviewed-on: https://forge.ops.eblu.me/eblume/blumeops/pulls/208

nixos/ringtail/flake.nix

@@ -1,5 +1,5 @@
 {
-  description = "NixOS configuration for ringtail (gaming/compute workstation)";
+  description = "NixOS configuration for ringtail (service host & gaming PC)";
 
   inputs = {
     nixpkgs.url = "github:NixOS/nixpkgs/nixos-25.11";
@@ -7,13 +7,18 @@
       url = "github:nix-community/disko";
       inputs.nixpkgs.follows = "nixpkgs";
     };
+    home-manager = {
+      url = "github:nix-community/home-manager/release-25.11";
+      inputs.nixpkgs.follows = "nixpkgs";
+    };
   };
 
-  outputs = { nixpkgs, disko, ... }: {
+  outputs = { nixpkgs, disko, home-manager, ... }: {
     nixosConfigurations.ringtail = nixpkgs.lib.nixosSystem {
       system = "x86_64-linux";
       modules = [
         disko.nixosModules.disko
+        home-manager.nixosModules.home-manager
         ./disk-config.nix
         ./hardware-configuration.nix
         ./configuration.nix