bug(util): truncateMiddle returns full string when maxLength <= 2 due to slice(-0) #20880

Description

truncateMiddle in packages/util/src/path.ts (and the identical implementation in packages/opencode/src/util/locale.ts) has an edge case bug when maxLength is 1 or 2.

When maxLength <= 2, end = Math.floor((maxLength - 1) / 2) evaluates to 0. The function then calls text.slice(-0), which in JavaScript is equivalent to text.slice(0) — returning the entire string rather than an empty suffix. The output therefore far exceeds maxLength.

Steps to reproduce

import { truncateMiddle } from "@opencode/util/path"

truncateMiddle("abcdefghijklmnop", 2)
// Expected: "a…"  (2 chars)
// Actual:   "a…abcdefghijklmnop"  (18 chars)

truncateMiddle("abcdefghijklmnop", 1)
// Expected: "…"   (1 char)
// Actual:   "…abcdefghijklmnop"  (17 chars)

Root cause

-0 === 0 in JavaScript, and String.prototype.slice treats -0 as 0, returning the full string.

Fix: guard the suffix slice — end > 0 ? text.slice(-end) : "".

The same bug is present in Locale.truncateMiddle in packages/opencode/src/util/locale.ts.