Manager: Add tags property to GroupEntry objects

What I did

I edited the code converting the story index to story hashes for use in the manager (transformStoryIndexToStoriesHash), to add a tags property for 'group' entries, which is the intersection of all their stories' hashes.

This is the 'group' counterpart of https://github.com/storybookjs/storybook/pull/29343. I am opening the PR because users of my addon have come to me requesting support for badges in group entries of the sidebar, which requires that tags are also computed for these: https://github.com/Sidnioulz/storybook-addon-tag-badges/issues/20.

Checklist for Contributors

Testing

The changes in this PR are covered in the following automated tests:

[ ] stories
[x] unit tests
[ ] integration tests
[ ] end-to-end tests

Manual testing

This section is mandatory for all contributions. If you believe no manual test is necessary, please state so explicitly. Thanks!

Add a sidebar renderLabel function that prints all tags
Notice the presence of 'dev', 'vitest', etc. tags in group entries in the storybook:ui instance

Documentation

Still not sure how/where to document this, like I pointed out in the component PR.

Checklist for Maintainers

[ ] When this PR is ready for testing, make sure to add ci:normal, ci:merged or ci:daily GH label to it to run a specific set of sandboxes. The particular set of sandboxes can be found in code/lib/cli-storybook/src/sandbox-templates.ts
[ ] Make sure this PR contains one of the labels below:

Available labels
- `bug`: Internal changes that fixes incorrect behavior. - `maintenance`: User-facing maintenance tasks. - `dependencies`: Upgrading (sometimes downgrading) dependencies. - `build`: Internal-facing build tooling & test updates. Will not show up in release changelog. - `cleanup`: Minor cleanup style change. Will not show up in release changelog. - `documentation`: Documentation **only** changes. Will not show up in release changelog. - `feature request`: Introducing a new feature. - `BREAKING CHANGE`: Changes that break compatibility in some way with current major version. - `other`: Changes that don't fit in the above categories.

🦋 Canary release

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_core team members can create a canary release here or locally with gh workflow run --repo storybookjs/storybook canary-release-pr.yml --field pr=<PR_NUMBER>_

Greptile Summary

Added support for tags in GroupEntry objects within the Storybook manager's sidebar, computing them as the intersection of child stories' tags.

Added tags property to API_GroupEntry interface in code/core/src/types/modules/api-stories.ts
Enhanced intersect utility in code/core/src/manager-api/lib/intersect.ts with stricter array validation
Modified transformStoryIndexToStoriesHash in code/core/src/manager-api/lib/stories.ts to compute group entry tags
Added unit tests in code/core/src/manager-api/tests/stories.test.ts verifying tag inheritance for group entries

storybookjs / storybook