feat: add hm-options package for Home Manager options

Add a new MCP server for Home Manager options, mirroring the
functionality of nixos-options but targeting the home-manager
repository.

Changes:
- Add shared options.Indexer interface for both implementations
- Add internal/homemanager package with indexer and channel aliases
- Add cmd/hm-options CLI entry point
- Parameterize MCP server with ServerConfig for name/instructions
- Parameterize nix/package.nix for building both packages
- Add hm-options package and NixOS module to flake.nix
- Add nix/hm-options-module.nix for systemd deployment

Co-Authored-By: Claude Opus 4.5 <noreply@anthropic.com>

flake.nix

@@ -19,6 +19,13 @@
         in
         {
           nixos-options = pkgs.callPackage ./nix/package.nix { src = ./.; };
+          hm-options = pkgs.callPackage ./nix/package.nix {
+            src = ./.;
+            pname = "hm-options-mcp";
+            subPackage = "cmd/hm-options";
+            mainProgram = "hm-options";
+            description = "MCP server for Home Manager options search and query";
+          };
           default = self.packages.${system}.nixos-options;
         });
 
@@ -50,6 +57,10 @@
           imports = [ ./nix/module.nix ];
           services.nixos-options-mcp.package = lib.mkDefault self.packages.${pkgs.system}.nixos-options;
         };
+        hm-options-mcp = { pkgs, ... }: {
+          imports = [ ./nix/hm-options-module.nix ];
+          services.hm-options-mcp.package = lib.mkDefault self.packages.${pkgs.system}.hm-options;
+        };
         default = self.nixosModules.nixos-options-mcp;
       };
     };