Use lazy import for quart.Response in sexp_response helper

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

shared/sexp/helpers.py

@@ -9,7 +9,6 @@ from __future__ import annotations
 from typing import Any
 
 from markupsafe import escape
-from quart import Response
 
 from .jinja_bridge import render
 from .page import SEARCH_HEADERS_MOBILE, SEARCH_HEADERS_DESKTOP
@@ -227,7 +226,7 @@ def full_page(ctx: dict, *, header_rows_html: str,
 
 
 def sexp_response(sexp_source: str, status: int = 200,
-                   headers: dict | None = None) -> Response:
+                   headers: dict | None = None):
     """Return an s-expression wire-format response.
 
     The client-side sexp.js will intercept responses with Content-Type
@@ -237,6 +236,7 @@ def sexp_response(sexp_source: str, status: int = 200,
 
         return sexp_response('(~test-row :nodeid "test_foo" :outcome "passed")')
     """
+    from quart import Response
     resp = Response(sexp_source, status=status, content_type="text/sexp")
     if headers:
         for k, v in headers.items():