Cherry-pick from ChatTwo upstream f35b7d3 (Infiziert90, 2026-05-12).
Chat.SetChannel allocates a native Utf8String for the target name and
then runs a validity check. The previous early return on an invalid
linkshell skipped Dtor and leaked the native allocation; every invalid
linkshell switch added one Utf8String to the unmanaged heap.
- Renamed ValidAnyLinkshell to IsChannelOrExistingLinkshell so the
call-site reads naturally.
- Wrapped ChangeChatChannel in the validity check instead of
early-returning. Dtor now runs on every path.
- ChatLogWindow follows the rename at its single call-site.
JonKazama-Hellion
db48f27842