Add sandboxed-workspace module for isolated dev environments

Provides isolated development environments using either VMs (microvm.nix)
or containers (systemd-nspawn) with a unified configuration interface.

Features:
- Unified options with required type field ("vm" or "container")
- Shared base configuration for networking, SSH, users, packages
- Automatic SSH host key generation and persistence
- Shell aliases for workspace management (start/stop/status/ssh)
- Automatic /etc/hosts entries for workspace hostnames
- restartIfChanged support for both VMs and containers
- Passwordless doas in workspaces

Container backend:
- Uses hostBridge for proper bridge networking with /24 subnet
- systemd-networkd for IP configuration
- systemd-resolved for DNS

VM backend:
- TAP interface with deterministic MAC addresses
- virtiofs shares for workspace directories
- vsock CID generation

common/sandboxed-workspace/home.nix

@@ -0,0 +1,50 @@
+{ config, lib, pkgs, ... }:
+
+# Home Manager configuration for sandboxed workspace user environment
+# This sets up the shell and tools inside VMs and containers
+
+{
+  home.username = "googlebot";
+  home.homeDirectory = "/home/googlebot";
+  home.stateVersion = "24.11";
+
+  programs.home-manager.enable = true;
+
+  # Shell configuration
+  programs.fish.enable = true;
+  programs.starship.enable = true;
+  programs.starship.enableFishIntegration = true;
+  programs.starship.settings.container.disabled = true;
+
+  # Basic command-line tools
+  programs.btop.enable = true;
+  programs.ripgrep.enable = true;
+  programs.eza.enable = true;
+
+  # Git configuration
+  programs.git = {
+    enable = true;
+    settings = {
+      user.name = lib.mkDefault "googlebot";
+      user.email = lib.mkDefault "zuckerberg@neet.dev";
+    };
+  };
+
+  # Shell aliases
+  home.shellAliases = {
+    ls = "eza";
+    la = "eza -la";
+    ll = "eza -l";
+  };
+
+  # Environment variables for Claude Code
+  home.sessionVariables = {
+    # Isolate Claude config to a specific directory on the host
+    CLAUDE_CONFIG_DIR = "/home/googlebot/claude-config";
+  };
+
+  # Additional packages for development
+  home.packages = with pkgs; [
+    # Add packages as needed per workspace
+  ];
+}