Fix mixed changeset blocking npm publish

[martin-henz]

Summary

• .changeset/stepper-hover-text-popover.md declared a patch bump for both @sourceacademy/common-stepper and @sourceacademy/web-stepper.
• web-stepper is in .changeset/config.json's ignore list (bundled host plugin, not published to npm — same treatment as web-data-visualizer), so changesets rejects any changeset that mixes an ignored and non-ignored package.
• This was hard-blocking yarn changeset version/publish on every push to main since the "Version Packages" PR (Version Packages #91) merged — nothing has published to npm.

Fix: drop web-stepper from this changeset, keeping the common-stepper bump.

Test plan

• CI build/tests pass
• Merge, then confirm the next on_push run's "Create Release Pull Request or Publish to npm" step succeeds (or opens a fresh Version Packages PR)

[changeset-bot]

⚠️ No Changeset found

Latest commit: 44c5328

Merging this PR will not cause a version bump for any packages. If these changes should not result in a new version, you're good to go. If these changes should result in a version bump, you need to add a changeset.

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💥 An error occurred when fetching the changed packages and changesets in this PR

Some errors occurred when validating the changesets config:
The package or glob expression "@sourceacademy/web-stepper" is specified in the `ignore` option but it is not found in the project. You may have misspelled the package name or provided an invalid glob expression. Note that glob expressions must be defined according to https://www.npmjs.com/package/micromatch
The package or glob expression "@sourceacademy/web-data-visualizer" is specified in the `ignore` option but it is not found in the project. You may have misspelled the package name or provided an invalid glob expression. Note that glob expressions must be defined according to https://www.npmjs.com/package/micromatch