feat(nixos): consolidate hosts into a shared flake

Manage T450s, X1EG2 and Framework 13 from pinned NixOS inputs while retaining
machine-specific storage and hardware configuration.

Changes:

Shared Configuration:
- Extract common, KDE, desktop, development and Steam modules
- Share Emacs, VS Code, htop, DevOps tools and Docker across hosts
- Remove obsolete apps and global project language runtimes

Framework:
- Import the 11th-generation Intel hardware profile
- Enable Steam and ZFS with tookland/home mounted at /home
- Document manual ext4 root and ZFS installation steps
- Require installer-generated hardware configuration before installation

Validation:
- Evaluate both ThinkPads and Framework with test hardware
- Check Nix syntax, formatting and whitespace

modules/development.nix

@@ -0,0 +1,48 @@
+{ pkgs, ... }:
+{
+  # Workstation tools only; language runtimes and SDKs belong in projects.
+  environment.systemPackages = with pkgs; [
+    # Editors and shell utilities.
+    emacs
+    vscode
+    git
+    htop
+    tmux
+    ripgrep
+    fd
+    duf
+    dust
+    killall
+    lsof
+    rsync
+    unzip
+    zip
+
+    # Infrastructure, containers, and structured data.
+    ansible
+    awscli2
+    docker-compose
+    jq
+    yq-go
+
+    # Networking and security tools.
+    openssh
+    gnupg
+    openssl
+    curl
+    dig
+    mosh
+    tcpdump
+    wget
+    whois
+    wireguard-tools
+  ];
+
+  virtualisation.docker.enable = true;
+  users.users.clw.extraGroups = [ "docker" ];
+
+  programs.direnv = {
+    enable = true;
+    nix-direnv.enable = true;
+  };
+}