* fix(channels): keep Feishu cards within the card size limit
Card text was unbounded and ASCII-escaped, so an answer of about 4,400 CJK
characters made the card request body exceed Feishu's 30 KB limit (230025).
The final patch and its reply fallback were both rejected, the answer was
lost and the running card stayed on its last streamed text.
Cards are now serialized without ASCII escapes and budgeted by the bytes
their text adds to the request body. A streamed update shows what fits; a
longer final answer continues in up to 10 cards replied to the same source
message, split at line breaks, and a retry resumes after the cards already
delivered.
* docs(changelog): reference #7798 for the Feishu card size fix
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Co-authored-by: Willem Jiang <willem.jiang@gmail.com>