## Context

The size check workflow's guided tour detection matches text inside HTML
comment placeholders in the PR template (e.g., `<!-- provide a guided
tour — numbered list of files/commits to read in order -->`), producing
false positives like the one on #51957.

Fix: strip `<!-- -->` comments from the PR body before running the
regex.

## How to Review

- Single file: `.github/workflows/pr-size-check.yml`, lines 148-151
- The `.replace(/<!--[\s\S]*?-->/g, '')` runs in `actions/github-script`
JS, not shell

## Self-Review Checklist

- [x] I've reviewed my own diff for quality, security, and reliability
- [x] Unsafe blocks (if any) have justifying comments
- [x] The content is consistent with the [UI/UX
checklist](https://github.com/zed-industries/zed/blob/main/CONTRIBUTING.md#uiux-checklist)
- [x] Tests cover the new/changed behavior
- [x] Performance impact has been considered and is acceptable

Release Notes:

- N/A