feat(home): Add starship cross-shell prompt role

Add a new home-manager role for starship.rs, a fast and customizable
cross-shell prompt written in Rust.

Configuration includes:
- Bash and Zsh integration enabled
- Clean character symbols (> for success, x for error)
- Vi mode indicator support
- Smart directory truncation (4 levels, truncate to repo root)
- Git branch and status display
- Nix shell indicator with snowflake symbol
- Command duration for long-running commands (2s+)
- Disabled noisy modules (language runtimes, cloud providers)

Enabled in: home-desktop, home-laptop-compact, home-live-usb,
home-media-center configurations.

Closes: nixos-configs-uji

home/home-desktop.nix

@@ -23,6 +23,7 @@
     kubectl.enable = true;
     tmux.enable = true;
     plasma-manager.enable = true;
+    starship.enable = true;
   };
 
   targets.genericLinux.enable = true;

home/home-laptop-compact.nix

@@ -23,6 +23,7 @@
     plasma-manager.enable = true;
     emacs.enable = true;
     i3_sway.enable = true;
+    starship.enable = true;
 
     # Launcher wrappers for excluded/optional packages
     launchers = {

home/home-live-usb.nix

@@ -16,6 +16,7 @@
     plasma-manager.enable = true;
     emacs.enable = true;
     i3_sway.enable = true;
+    starship.enable = true;
     # development.enable = false;  # Not needed for live USB
     # communication.enable = false; # Not needed for live USB
     # office.enable = false;       # Not needed for live USB

home/home-media-center.nix

@@ -20,6 +20,7 @@
     plasma-manager.enable = true;
     emacs.enable = true;
     i3_sway.enable = true;
+    starship.enable = true;
     # office.enable = false;    # Not needed for media center
     # sync.enable = false;      # Shared machine, no personal file sync
   };

home/roles/default.nix

@@ -19,5 +19,6 @@
     ./sync
     ./tmux
     ./emacs
+    ./starship
   ];
 }

home/roles/starship/default.nix

@@ -0,0 +1,72 @@
+{ config, lib, pkgs, ... }:
+
+with lib;
+
+let
+  cfg = config.home.roles.starship;
+in
+{
+  options.home.roles.starship = {
+    enable = mkEnableOption "starship cross-shell prompt";
+  };
+
+  config = mkIf cfg.enable {
+    programs.starship = {
+      enable = true;
+      enableBashIntegration = true;
+      enableZshIntegration = true;
+
+      settings = {
+        add_newline = true;
+
+        character = {
+          success_symbol = "[>](bold green)";
+          error_symbol = "[x](bold red)";
+          vimcmd_symbol = "[<](bold green)";
+        };
+
+        directory = {
+          truncation_length = 4;
+          truncate_to_repo = true;
+        };
+
+        git_branch = {
+          symbol = "";
+          format = "[$symbol$branch(:$remote_branch)]($style) ";
+        };
+
+        git_status = {
+          format = "([$all_status$ahead_behind]($style) )";
+        };
+
+        nix_shell = {
+          symbol = "";
+          format = "[$symbol$state( \\($name\\))]($style) ";
+        };
+
+        cmd_duration = {
+          min_time = 2000;
+          format = "[$duration]($style) ";
+        };
+
+        # Disable modules that are noisy or rarely needed
+        package.disabled = true;
+        nodejs.disabled = true;
+        python.disabled = true;
+        ruby.disabled = true;
+        java.disabled = true;
+        golang.disabled = true;
+        rust.disabled = true;
+        php.disabled = true;
+        lua.disabled = true;
+        perl.disabled = true;
+        terraform.disabled = true;
+        kubernetes.disabled = true;
+        docker_context.disabled = true;
+        aws.disabled = true;
+        gcloud.disabled = true;
+        azure.disabled = true;
+      };
+    };
+  };
+}