fix(dingtalk): repair _extract_text for dingtalk-stream >= 0.20 SDK shape

The cherry-picked SDK compat fix (previous commit) wired process() to
parse CallbackMessage.data into a ChatbotMessage, but _extract_text()
was still written against the pre-0.20 payload shape:

  * message.text changed from dict {content: ...} → TextContent object.
    The old code's str(text) fallback produced 'TextContent(content=...)'
    as the agent's input, so every received message came in mangled.
  * rich_text moved from message.rich_text (list) to
    message.rich_text_content.rich_text_list.

This preserves legacy fallbacks (dict-shaped text, bare rich_text list)
while handling the current SDK layout via hasattr(text, 'content').

Adds regression tests covering:
  * webhook domain allowlist (api.*, oapi.*, and hostile lookalikes)
  * _IncomingHandler.process is a coroutine function
  * _extract_text against TextContent object, dict, rich_text_content,
    legacy rich_text, and empty-message cases

Also adds kevinskysunny to scripts/release.py AUTHOR_MAP (release CI
blocks unmapped emails).

scripts/release.py

@@ -82,6 +82,7 @@ AUTHOR_MAP = {
     "xaydinoktay@gmail.com": "aydnOktay",
     "abdullahfarukozden@gmail.com": "Farukest",
     "lovre.pesut@gmail.com": "rovle",
+    "kevinskysunny@gmail.com": "kevinskysunny",
     "hakanerten02@hotmail.com": "teyrebaz33",
     "ruzzgarcn@gmail.com": "Ruzzgar",
     "alireza78.crypto@gmail.com": "alireza78a",