* fix(config): use truncateUtf16Safe for allowed-values hint text
Replace naive .slice(0, N) with truncateUtf16Safe() to prevent
surrogate pair splitting in config validation hint messages
shown to users.
Co-Authored-By: Claude <noreply@anthropic.com>
* test(config): prove UTF-16 allowed-value hint boundary
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Co-authored-by: Claude <noreply@anthropic.com>
Co-authored-by: Peter Steinberger <steipete@gmail.com>