fix(ui): escape html in error diff

[hi-ogawa]

Description

• Closes HTML content in test report is not escaped properly in VItest UI #5321
• Related fix(ui): escape html for console log view #4724

I applied the same fix as #4724 for error.diff this time.

Screenshots before and after

• before

• after

Please don't delete this checklist! Before submitting the PR, please make sure you do the following:

• It's really useful if your PR references an issue where it is discussed ahead of time. If the feature is substantial or introduces breaking changes without a discussion, PR might be closed.
• Ideally, include a test that fails without this PR but passes with it.
• Please, don't make changes to pnpm-lock.yaml unless you introduce a new test example.

Tests

• Run the tests with pnpm test:ci.

Documentation

• If you introduce new functionality, document it. You can run documentation with pnpm run docs command.

Changesets

• Changes in changelog are generated from PR name. Please, make sure that it explains your changes in an understandable manner. Please, prefix changeset messages with feat:, fix:, perf:, docs:, or chore:.

[netlify]

✅ Deploy Preview for fastidious-cascaron-4ded94 canceled.

Name	Link
🔨 Latest commit	770a00d
🔍 Latest deploy log	https://app.netlify.com/sites/fastidious-cascaron-4ded94/deploys/65e2c2410e4b5e00098b92c1