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

hosts/framework/configuration.nix

@@ -0,0 +1,39 @@
+{ ... }:
+{
+  imports = [
+    ./hardware-configuration.nix
+    ../../modules/common.nix
+    ../../modules/kde.nix
+    ../../modules/development.nix
+    ../../modules/gaming.nix
+  ];
+
+  nixpkgs.hostPlatform = "x86_64-linux";
+  networking.hostName = "framework";
+  # Stable, unique ID required by ZFS; keep it unchanged after pool creation.
+  networking.hostId = "fdc3ff7d";
+  boot.loader.systemd-boot.enable = true;
+  boot.loader.efi.canTouchEfiVariables = true;
+
+  # Framework 13, Intel Core i5-1135G7. Hardware tuning comes from nixos-hardware.
+  services.fwupd.enable = true;
+
+  # Existing pool/dataset must be created in the installer; root stays ext4.
+  boot.supportedFilesystems = [ "zfs" ];
+  boot.zfs.extraPools = [ "tookland" ];
+  boot.zfs.forceImportRoot = false;
+  fileSystems."/home" = {
+    device = "tookland/home";
+    fsType = "zfs";
+    # Mount home before activation creates user directories.
+    neededForBoot = true;
+  };
+  services.zfs.autoScrub.enable = true;
+
+  # A simple laptop policy using Plasma's power management integration.
+  services.power-profiles-daemon.enable = true;
+  services.libinput.enable = true;
+
+  # First installation release; keep this unchanged after installation.
+  system.stateVersion = "26.05";
+}