fix(gateway): accept finalize kwarg in all platform edit_message overrides

stream_consumer._send_or_edit unconditionally passes finalize= to
adapter.edit_message(), but only DingTalk's override accepted the
kwarg. Streaming on Telegram/Discord/Slack/Matrix/Mattermost/Feishu/
WhatsApp raised TypeError the first time a segment break or final
edit fired.

The REQUIRES_EDIT_FINALIZE capability flag only gates the redundant
final edit (and the identical-text short-circuit), not the kwarg
itself — so adapters that opt out of finalize still receive the
keyword argument and must accept it.

Add *, finalize: bool = False to the 7 non-DingTalk signatures; the
body ignores the arg since those platforms treat edits as stateless
(consistent with the base class contract in base.py).

Add a parametrized signature check over every concrete adapter class
so a future override cannot silently drop the kwarg — existing tests
use MagicMock which swallows any kwarg and cannot catch this.

Fixes #12579

tests/gateway/test_stream_consumer.py

@@ -133,6 +133,43 @@ class TestFinalizeCapabilityGate:
         assert picky.edit_message.call_args[1]["finalize"] is True
 
 
+class TestEditMessageFinalizeSignature:
+    """Every concrete platform adapter must accept the ``finalize`` kwarg.
+
+    stream_consumer._send_or_edit always passes ``finalize=`` to
+    ``adapter.edit_message(...)`` (see gateway/stream_consumer.py).  An
+    adapter that overrides edit_message without accepting finalize raises
+    TypeError the first time streaming hits a segment break or final edit.
+    Guard the contract with an explicit signature check so it cannot
+    silently regress — existing tests use MagicMock which swallows any
+    kwarg and cannot catch this.
+    """
+
+    @pytest.mark.parametrize(
+        "module_path,class_name",
+        [
+            ("gateway.platforms.telegram", "TelegramAdapter"),
+            ("gateway.platforms.discord", "DiscordAdapter"),
+            ("gateway.platforms.slack", "SlackAdapter"),
+            ("gateway.platforms.matrix", "MatrixAdapter"),
+            ("gateway.platforms.mattermost", "MattermostAdapter"),
+            ("gateway.platforms.feishu", "FeishuAdapter"),
+            ("gateway.platforms.whatsapp", "WhatsAppAdapter"),
+            ("gateway.platforms.dingtalk", "DingTalkAdapter"),
+        ],
+    )
+    def test_edit_message_accepts_finalize(self, module_path, class_name):
+        import inspect
+
+        module = pytest.importorskip(module_path)
+        cls = getattr(module, class_name)
+        params = inspect.signature(cls.edit_message).parameters
+        assert "finalize" in params, (
+            f"{class_name}.edit_message must accept 'finalize' kwarg; "
+            f"stream_consumer._send_or_edit passes it unconditionally"
+        )
+
+
 class TestSendOrEditMediaStripping:
     """Verify _send_or_edit strips MEDIA: before sending to the platform."""