Add Nix flake for mcrctl

Vendor dependencies and expose mcrctl binary via nix build.

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

vendor/github.com/go-chi/chi/v5/middleware/clean_path.go

@@ -0,0 +1,28 @@
+package middleware
+
+import (
+	"net/http"
+	"path"
+
+	"github.com/go-chi/chi/v5"
+)
+
+// CleanPath middleware will clean out double slash mistakes from a user's request path.
+// For example, if a user requests /users//1 or //users////1 will both be treated as: /users/1
+func CleanPath(next http.Handler) http.Handler {
+	return http.HandlerFunc(func(w http.ResponseWriter, r *http.Request) {
+		rctx := chi.RouteContext(r.Context())
+
+		routePath := rctx.RoutePath
+		if routePath == "" {
+			if r.URL.RawPath != "" {
+				routePath = r.URL.RawPath
+			} else {
+				routePath = r.URL.Path
+			}
+			rctx.RoutePath = path.Clean(routePath)
+		}
+
+		next.ServeHTTP(w, r)
+	})
+}