feat: add package indexing to MCP index_revision tool

The options server's index_revision now also indexes packages when running
under nixpkgs-search, matching the CLI behavior. The packages server gets
its own index_revision tool for standalone package indexing.

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

cmd/nixpkgs-search/main.go

@@ -20,7 +20,7 @@ import (
 
 const (
 	defaultDatabase = "sqlite://nixpkgs-search.db"
-	version         = "0.3.0"
+	version         = "0.4.0"
 )
 
 func main() {
@@ -310,7 +310,8 @@ func runOptionsServe(c *cli.Context) error {
 	server := mcp.NewServer(store, logger, config)
 
 	indexer := nixos.NewIndexer(store)
-	server.RegisterHandlers(indexer)
+	pkgIndexer := packages.NewIndexer(store)
+	server.RegisterHandlersWithPackages(indexer, pkgIndexer)
 
 	transport := c.String("transport")
 	switch transport {