Fix mypy and pylint issues introduced by the xtractmime merge

- Add xtractmime to the mypy ignore_missing_imports overrides (no py.typed
  marker in that library)
- Narrow Content-Disposition header via a local variable so mypy can see
  it is non-None inside the if-block
- Remove a redundant local re-import of HtmlResponse/TextResponse inside
  open_in_browser (they are already imported at module level, fixing
  pylint W0404 reimported)
- Add Any annotations to _unmark() in test_responsetypes.py so mypy does
  not raise no-untyped-call when it is called from a typed context

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

pyproject.toml

@@ -133,6 +133,8 @@ module = [
     "pytest_twisted",
     "robotexclusionrulesparser",
     "testfixtures",
+    "xtractmime",
+    "xtractmime.*",
     "zope.interface.*",
 ]
 ignore_missing_imports = true

scrapy/utils/response.py

@@ -94,13 +94,10 @@ def _get_encoding_or_mime_type_from_headers(
         )
     ):
         return None, headers[b"Content-Type"]
-    if headers.get(b"Content-Disposition"):
+    content_disposition = headers.get(b"Content-Disposition")
+    if content_disposition:
         path = (
-            headers[b"Content-Disposition"]
-            .split(b";")[-1]
-            .split(b"=")[-1]
-            .strip(b"\"'")
-            .decode()
+            content_disposition.split(b";")[-1].split(b"=")[-1].strip(b"\"'").decode()
         )
         encoding, mime_type = _get_encoding_or_mime_type_from_path(path)
         if encoding:
@@ -262,9 +259,6 @@ def open_in_browser(
             if "item name" not in response.body:
                 open_in_browser(response)
     """
-    # circular imports
-    from scrapy.http import HtmlResponse, TextResponse  # noqa: PLC0415
-
     # XXX: this implementation is a bit dirty and could be improved
     body = response.body
     if isinstance(response, HtmlResponse):

tests/test_responsetypes.py

@@ -1,3 +1,7 @@
+from __future__ import annotations
+
+from typing import Any
+
 import pytest
 
 from scrapy.http import (
@@ -13,7 +17,7 @@ from scrapy.responsetypes import responsetypes
 from .test_utils_response import POST_XTRACTMIME_SCENARIOS, PRE_XTRACTMIME_SCENARIOS
 
 
-def _unmark(item):
+def _unmark(item: Any) -> Any:
     return pytest.param(*item.values)