fix: Response.json() honors declared charset

Routes the body through self.text instead of json.loads(self.content),
so a declared charset (e.g. iso-8859-1) is respected before JSON
parsing. ASCII / UTF-8 bodies are unchanged. Docstring now explicitly
documents the json.JSONDecodeError raise contract.

Wrapping JSONDecodeError in a domain exception is left to a future
response-API revision.

Closes deferred-work entries: "Response.json() raises raw and ignores
charset" (retro) and "Response.json() honor declared charset" (1-2).

Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>

Author: lesnik512

src/httpware/response.py

@@ -48,8 +48,13 @@ def text(self) -> str:
             return self.content.decode("utf-8")
 
     def json(self) -> Any:  # noqa: ANN401
-        """Parse `content` as JSON."""
-        return json.loads(self.content)
+        """Parse `content` as JSON using the declared charset (default UTF-8).
+
+        Raises:
+            json.JSONDecodeError: if the body is not valid JSON.
+
+        """
+        return json.loads(self.text)
 
     def with_headers(self, headers: Mapping[str, str]) -> Self:
         """Return a copy with the given headers merged in (incoming keys override existing)."""

tests/test_response.py

@@ -84,6 +84,18 @@ def test_response_json_parses_body() -> None:
     assert resp.json() == {"a": 1, "b": [2, 3]}
 
 
+def test_response_json_uses_declared_charset() -> None:
+    body = '{"name": "café"}'.encode("iso-8859-1")
+    resp = Response(
+        status=HTTPStatus.OK,
+        headers={"content-type": "application/json; charset=iso-8859-1"},
+        content=body,
+        url="/",
+        elapsed=0.0,
+    )
+    assert resp.json() == {"name": "café"}
+
+
 def test_response_equality_on_identical_fields() -> None:
     r1 = Response(status=200, headers={"a": "1"}, content=b"x", url="/", elapsed=0.5)
     r2 = Response(status=200, headers={"a": "1"}, content=b"x", url="/", elapsed=0.5)