* fix(irc): chunk PRIVMSG on UTF-16 boundary to avoid lone surrogates
sendPrivmsg split long messages with String.slice on a UTF-16 code-unit
index, so an emoji (or other astral character) straddling the split
point was cut into a lone high/low surrogate, sending broken bytes in
the PRIVMSG to the IRC server.
Slice each chunk with sliceUtf16Safe so a surrogate pair is never split.
When the budget is too small to fit even the leading astral character,
emit that character whole so chunking still makes progress.
Adds a socket-level test (fake net/tls socket) asserting no PRIVMSG
chunk contains a lone surrogate, including the one-code-unit budget
edge case, while the existing space-preferring split is preserved.
* refactor(irc): make surrogate-safe chunking direct
* fix(irc): preserve one-unit chunk limits
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Co-authored-by: Peter Steinberger <steipete@gmail.com>
685c22dfb7