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>

internal/mcp/server_test.go

@@ -14,7 +14,7 @@ import (
 
 func TestServerInitialize(t *testing.T) {
 	store := setupTestStore(t)
-	server := NewServer(store, nil)
+	server := NewServer(store, nil, DefaultNixOSConfig())
 
 	input := `{"jsonrpc":"2.0","id":1,"method":"initialize","params":{"protocolVersion":"2024-11-05","capabilities":{},"clientInfo":{"name":"test","version":"1.0"}}}`
 
@@ -41,7 +41,7 @@ func TestServerInitialize(t *testing.T) {
 
 func TestServerToolsList(t *testing.T) {
 	store := setupTestStore(t)
-	server := NewServer(store, nil)
+	server := NewServer(store, nil, DefaultNixOSConfig())
 
 	input := `{"jsonrpc":"2.0","id":1,"method":"tools/list"}`
 
@@ -93,7 +93,7 @@ func TestServerToolsList(t *testing.T) {
 
 func TestServerMethodNotFound(t *testing.T) {
 	store := setupTestStore(t)
-	server := NewServer(store, nil)
+	server := NewServer(store, nil, DefaultNixOSConfig())
 
 	input := `{"jsonrpc":"2.0","id":1,"method":"unknown/method"}`
 
@@ -110,7 +110,7 @@ func TestServerMethodNotFound(t *testing.T) {
 
 func TestServerParseError(t *testing.T) {
 	store := setupTestStore(t)
-	server := NewServer(store, nil)
+	server := NewServer(store, nil, DefaultNixOSConfig())
 
 	input := `not valid json`
 
@@ -127,7 +127,7 @@ func TestServerParseError(t *testing.T) {
 
 func TestServerNotification(t *testing.T) {
 	store := setupTestStore(t)
-	server := NewServer(store, nil)
+	server := NewServer(store, nil, DefaultNixOSConfig())
 
 	// Notification (no response expected)
 	input := `{"jsonrpc":"2.0","method":"notifications/initialized"}`
@@ -254,7 +254,7 @@ func setupTestStore(t *testing.T) database.Store {
 func setupTestServer(t *testing.T, store database.Store) *Server {
 	t.Helper()
 
-	server := NewServer(store, nil)
+	server := NewServer(store, nil, DefaultNixOSConfig())
 	indexer := nixos.NewIndexer(store)
 	server.RegisterHandlers(indexer)