feat: link dotfiles via Home Manager and add NVMe install guide

Co-authored-by: aider (openrouter/openai/gpt-5.2) <aider@aider.chat>

home/sam/home.nix

@@ -1,5 +1,14 @@
 { config, pkgs, ... }:
 
+let
+  # After install, Integral300 is mounted at /data (per your NixOS config).
+  # These dotfiles are stored on that drive.
+  dotfilesDir = "/data/home_sam_ubuntu/dotfiles";
+
+  # Home Manager helper to symlink files/dirs that live outside the Nix store.
+  # This is the correct mechanism for "dotfiles stored on /data".
+  mkOOS = config.lib.file.mkOutOfStoreSymlink;
+in
 {
   home.stateVersion = "24.05";
 
@@ -26,12 +35,24 @@
       tree = "eza --tree";
       cat = "bat --color=always --paging=never";
     };
+
+    # Dotfiles integration notes:
+    # - I am NOT symlinking ~/.zshrc directly because Home Manager manages it.
+    # - If you have extra Zsh snippets in your dotfiles repo that you want sourced,
+    #   tell me the exact filename(s) and we’ll add them here safely.
+    initExtra = ''
+      # Optional: source additional Zsh config from /data dotfiles if you want.
+      # Example (uncomment + adjust if you confirm the exact file path):
+      # if [ -f "${dotfilesDir}/zsh/extra.zsh" ]; then
+      #   source "${dotfilesDir}/zsh/extra.zsh"
+      # fi
+    '';
   };
 
   programs.powerlevel10k = {
     enable = true;
-    # Optional: link your p10k config once you add it to the repo
-    # home.file.".p10k.zsh".source = ./p10k.zsh;
+    # If you have a real p10k config file in dotfiles, tell me its exact path.
+    # Then we can symlink it to ~/.p10k.zsh (or source it) reliably.
   };
 
   # ---
@@ -89,6 +110,26 @@
     p7zip
   ];
 
+  # ---
+  # Dotfiles (out-of-store symlinks from /data)
+  # ---
+  # IMPORTANT:
+  # - These paths must exist on the machine at activation time.
+  # - This assumes your dotfiles are available at:
+  #     /data/home_sam_ubuntu/dotfiles/<app>
+  # - If you rename/move the dotfiles directory, update dotfilesDir above.
+  home.file.".config/atuin".source = mkOOS "${dotfilesDir}/atuin";
+  home.file.".config/kitty".source = mkOOS "${dotfilesDir}/kitty";
+  home.file.".config/nvim".source = mkOOS "${dotfilesDir}/nvim";
+  home.file.".config/zellij".source = mkOOS "${dotfilesDir}/zellij";
+
+  # TODO (needs confirmation from you):
+  # - zsh dotfiles: what exact files do you want sourced/linked?
+  # - pk10k: what is the exact filename for your p10k config?
+  #
+  # Once you confirm, we can add e.g.:
+  # home.file.".p10k.zsh".source = mkOOS "${dotfilesDir}/pk10k/.p10k.zsh";
+
   # ---
   # Secrets policy
   # ---