diffToDelta and patchToText can throw if diff split surrogate-pair

Describe the bug

The current diff implementation operates on UTF-16 characters directly, which can cause it to split surrogate-pairs. When this happens, diffToDelta and patchToText can throw URIError.

Reproducible on the latest v2.0.1.

Reproduction:

import { diff, diffToDelta, patch, patchToText } from 'diff-match-patch-es'

const oldText = '😀'
const newText = '😃'

const diffs = diff(oldText, newText)
console.log('diff:', JSON.stringify(diffs))

for (const [label, reproduce] of [
  ['diffToDelta', () => diffToDelta(diffs)],
  ['patchToText', () => patchToText(patch(oldText, newText))],
]) {
  try {
    console.log(`${label}:`, reproduce())
  } catch (error) {
    console.log(`${label}:`, `${error.name}: ${error.message}`)
  }
}

Output:

diff: [[0,"\ud83d"],[-1,"\ude00"],[1,"\ude03"]]
diffToDelta: URIError: URI malformed
patchToText: URIError: URI malformed

Reproduction

https://github.com/aforemendude/bugs-reproduction/tree/main/diff-match-patch-es-urierror

System Info

  System:
    OS: Linux 7.0 Ubuntu 24.04.4 LTS 24.04.4 LTS (Noble Numbat)
    CPU: (4) x64 Intel(R) N95
    Memory: 12.10 GB / 15.40 GB
    Container: Yes
    Shell: 5.2.21 - /bin/bash
  Binaries:
    Node: 24.18.0 - /usr/local/nodejs/bin/node
    npm: 11.16.0 - /usr/local/nodejs/bin/npm

Used Package Manager

npm

Validations

• Follow our Code of Conduct
• Read the Contributing Guide.
• Check that there isn't already an issue that reports the same bug to avoid creating a duplicate.
• Check that this is a concrete bug. For Q&A, please open a GitHub Discussion instead.
• The provided reproduction is a minimal reproducible of the bug.

Contributions

• I am willing to submit a PR to fix this issue
• I am willing to submit a PR with failing tests (actually just go ahead and do it, thanks!)

Start with the diff, diffToDelta, patch, and patchToText entry points shown in the reproduction, then run the provided surrogate-pair example. Trace how the split characters reach the URI encoding step; done means the example completes without URIError and preserves the expected diff and patch text.