chore: sync core lib and CLAUDE.md from agent-core

[avifenesh]

Automated sync of lib/ and CLAUDE.md from agent-core.

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Note

Low Risk
Low risk utility change, but it alters truncate semantics (code-point counting and maxLength<=0 behavior) which could slightly change truncated output in consumers.

Overview
Updates truncate in lib/cross-platform/index.js to truncate by Unicode code points (via spreading into an array) instead of UTF-16 code units, preventing broken surrogate pairs (e.g., emoji) in truncated strings.

Also changes edge-case handling so non-positive maxLength returns the original text unchanged, and clarifies the JSDoc to document code-point length semantics.

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Cursor Bugbot has reviewed your changes and found 1 potential issue.

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Negative slice index produces longer-than-original output

Medium Severity

When maxLength is 1 or 2, the expression maxLength - 3 becomes negative. Array.prototype.slice interprets a negative second argument as an offset from the end of the array, so it returns most of the array rather than an empty prefix. The resulting "truncated" string can be significantly longer than the input — the opposite of the function's purpose. The old code using substring didn't have this problem because substring clamps negatives to 0.

 

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