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>

nix/package.nix

@@ -1,26 +1,29 @@
-{ lib, buildGoModule, makeWrapper, nix, src }:
+{ lib, buildGoModule, makeWrapper, nix, src
+, pname ? "nixos-options-mcp"
+, subPackage ? "cmd/nixos-options"
+, mainProgram ? "nixos-options"
+, description ? "MCP server for NixOS options search and query"
+}:
 
 buildGoModule {
-  pname = "nixos-options-mcp";
+  inherit pname src;
   version = "0.1.0";
-  inherit src;
 
   vendorHash = "sha256-D0KIxQC9ctIAaHBFTvkhBE06uOZwDUcIw8471Ug2doY=";
 
-  subPackages = [ "cmd/nixos-options" ];
+  subPackages = [ subPackage ];
 
   nativeBuildInputs = [ makeWrapper ];
 
   postInstall = ''
-    wrapProgram $out/bin/nixos-options \
+    wrapProgram $out/bin/${mainProgram} \
       --prefix PATH : ${lib.makeBinPath [ nix ]}
   '';
 
   meta = with lib; {
-    description = "MCP server for NixOS options search and query";
+    inherit description mainProgram;
     homepage = "https://git.t-juice.club/torjus/labmcp";
     license = licenses.mit;
     maintainers = [ ];
-    mainProgram = "nixos-options";
   };
 }