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/nixos/indexer.go

@@ -16,6 +16,7 @@ import (
 	"time"
 
 	"git.t-juice.club/torjus/labmcp/internal/database"
+	"git.t-juice.club/torjus/labmcp/internal/options"
 )
 
 // revisionPattern validates revision strings to prevent injection attacks.
@@ -40,13 +41,8 @@ func NewIndexer(store database.Store) *Indexer {
 }
 
 // IndexResult contains the results of an indexing operation.
-type IndexResult struct {
-	Revision       *database.Revision
-	OptionCount    int
-	FileCount      int
-	Duration       time.Duration
-	AlreadyIndexed bool // True if revision was already indexed (skipped)
-}
+// Deprecated: Use options.IndexResult instead.
+type IndexResult = options.IndexResult
 
 // ValidateRevision checks if a revision string is safe to use.
 // Returns an error if the revision contains potentially dangerous characters.
@@ -305,7 +301,30 @@ func (idx *Indexer) getCommitDate(ctx context.Context, ref string) (time.Time, e
 	return commit.Commit.Committer.Date, nil
 }
 
-// resolveRevision resolves a channel name or ref to a git ref.
+// ResolveRevision resolves a channel name or ref to a git ref.
+func (idx *Indexer) ResolveRevision(revision string) string {
+	// Check if it's a known channel alias
+	if ref, ok := ChannelAliases[revision]; ok {
+		return ref
+	}
+	return revision
+}
+
+// GetChannelName returns the channel name if the revision matches one.
+func (idx *Indexer) GetChannelName(revision string) string {
+	if _, ok := ChannelAliases[revision]; ok {
+		return revision
+	}
+	// Check if the revision is a channel ref value
+	for name, ref := range ChannelAliases {
+		if ref == revision {
+			return name
+		}
+	}
+	return ""
+}
+
+// resolveRevision is a helper that calls the method.
 func resolveRevision(revision string) string {
 	// Check if it's a known channel alias
 	if ref, ok := ChannelAliases[revision]; ok {
@@ -314,7 +333,7 @@ func resolveRevision(revision string) string {
 	return revision
 }
 
-// getChannelName returns the channel name if the revision matches one.
+// getChannelName is a helper that returns the channel name.
 func getChannelName(revision string) string {
 	if _, ok := ChannelAliases[revision]; ok {
 		return revision