縮短標籤為何剩半個 emoji？

import {DatabaseSync} from 'node:sqlite';
import {TextDecoder} from 'node:util';
import {inflateSync} from 'node:zlib';
import {posix} from 'node:path';
import {createHash} from 'node:crypto';
const rows=(db,sql)=>db.prepare(sql).all().map(r=>({...r}));
const failed=(action)=>{try{action();return null;}catch(e){return {code:e.errcode??e.code??e.name};}};

import assert from 'node:assert/strict';
const run=function run(i,corrected=true){
    if(!Number.isInteger(i.limit)||i.limit<0)return {accepted:false,error:'invalid-limit'};
    const text=corrected?Array.from(i.text).slice(0,i.limit).join(''):i.text.slice(0,i.limit);
    return {text,codePoints:Array.from(text).map(c=>c.codePointAt(0)),source:i.text};
  };
const cases=[{"label":"misleading base","input":{"text":"A😀B","limit":2},"expected":{"text":"A\ud83d","codePoints":[65,55357],"source":"A😀B"},"corrected":false},{"label":"corrected base","input":{"text":"A😀B","limit":2},"expected":{"text":"A😀","codePoints":[65,128512],"source":"A😀B"},"corrected":true},{"label":"zero character allowance","input":{"text":"A😀B","limit":0},"expected":{"text":"","codePoints":[],"source":"A😀B"},"corrected":true},{"label":"exact full character length","input":{"text":"A😀B","limit":3},"expected":{"text":"A😀B","codePoints":[65,128512,66],"source":"A😀B"},"corrected":true}];
for(const test of cases){
  const actual=run(test.input,test.corrected);
  assert.deepEqual(actual,test.expected,test.label);
  console.log(test.label,actual);
}