CI: Remove obsolete test-storybooks-portable-vitest3 job and react-vitest-3 template

[obvious-autobuild]

What I did

The Vitest 4 floor raise (#36164) obsoleted the dedicated Vitest 3 kitchen-sink variant, but its CI step survived. This PR removes the dead weight:

• Deleted the definePortableStoryTestVitest3 job definition (job test-storybooks-portable-vitest3, Playwright E2E against test-storybooks/portable-stories-kitchen-sink/react-vitest-3) and its registration in getTestStorybooks() in scripts/ci/test-storybooks.ts.
• With the registration gone, getTestStorybooks no longer uses its workflow parameter — removed it (and the Workflow type import), updating the single call site in scripts/ci/main.ts.
• Deleted the orphaned test-storybooks/portable-stories-kitchen-sink/react-vitest-3/ template directory that this job exclusively consumed. The sibling variants (react, vue3, svelte, nextjs) and the MCP test-storybook are untouched.

No issue — orphaned by #36164.

Checklist for Contributors

Testing

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

• stories
• unit tests
• integration tests
• end-to-end tests

Manual testing

Caution

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

No manual browser testing is needed — this PR only touches CI config generation and removes a template directory; there is no runtime Storybook behavior change. What I validated instead:

1. Generated the CircleCI config for all four workflows (normal, merged, daily, docs) via yarn dlx jiti ./scripts/ci/main.ts --workflow=<workflow> before and after the change, and diffed:
   • normal and docs: byte-identical (the job was gated to merged and above).
   • merged and daily: 30 lines removed, 0 added — solely the test-storybooks-portable-vitest3 job definition, its workflow-list entry, and one inbound requires reference. No other job changed.
   • After the change, grep vitest3 finds 0 references in every generated config.
2. Repo-wide git grep for react-vitest-3, portable-vitest3, definePortableStoryTestVitest3 (excluding code/**/dist build output): no remaining references. The only Vitest3-pattern hits outside this diff are isVitest3_2To4 in compiled dist output of addon-vitest/create-storybook — legitimate runtime version-gating code, unrelated to this CI job.
3. tsc --noEmit -p scripts/tsconfig.json: zero errors under scripts/ (pre-existing errors in code/ are unchanged base-branch noise from that config's import graph).
4. oxlint and oxfmt --check on both touched files: clean.

To verify yourself: run yarn dlx jiti ./scripts/ci/main.ts --workflow=merged and confirm .circleci/config.generated.yml contains no test-storybooks-portable-vitest3 job.

Documentation

• Add or update documentation reflecting your changes
• If you are deprecating/removing a feature, make sure to update
  MIGRATION.MD

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

• Declare whether manual QA will be needed for this PR during the next release, through qa:needed or qa:skip

• 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 - 🚫 Not run

This PR does not have a canary release associated.

In-repo PRs: add the ci:canary label. Later pushes republish while the label remains.

Fork PRs: the label does nothing (a later push must not auto-publish). A maintainer publishes from this repository with Run workflow and the pr input. branch and sha are optional; if more than one is set, they must be the same commit. The fork author does not need to do anything.

🔗 Obvious Project · 🧵 Obvious Thread

[storybook-app-bot]

Package Benchmarks

^{Commit: 2af2182, ran on 14 September 2026 at 10:18:49 UTC}

The following packages have significant changes to their size or dependencies:

@storybook/builder-webpack5

	Before	After	Difference
Dependency count	182	181	🎉 -1 🎉
Self size	92 KB	92 KB	🎉 -96 B 🎉
Dependency size	37.75 MB	38.33 MB	🚨 +581 KB 🚨
Bundle Size Analyzer	Link	Link

@storybook/ember

	Before	After	Difference
Dependency count	181	180	🎉 -1 🎉
Self size	13 KB	13 KB	🎉 -18 B 🎉
Dependency size	33.07 MB	33.65 MB	🚨 +580 KB 🚨
Bundle Size Analyzer	Link	Link

@storybook/nextjs

	Before	After	Difference
Dependency count	447	447	0
Self size	641 KB	641 KB	0 B
Dependency size	61.37 MB	62.25 MB	🚨 +878 KB 🚨
Bundle Size Analyzer	Link	Link

@storybook/react-webpack5

	Before	After	Difference
Dependency count	267	266	🎉 -1 🎉
Self size	23 KB	23 KB	🎉 -12 B 🎉
Dependency size	50.29 MB	50.87 MB	🚨 +580 KB 🚨
Bundle Size Analyzer	Link	Link

@storybook/server-webpack5

	Before	After	Difference
Dependency count	194	193	🎉 -1 🎉
Self size	15 KB	15 KB	0 B
Dependency size	39.03 MB	39.61 MB	🚨 +580 KB 🚨
Bundle Size Analyzer	Link	Link

@storybook/preset-react-webpack

	Before	After	Difference
Dependency count	153	152	🎉 -1 🎉
Self size	14 KB	14 KB	0 B
Dependency size	34.41 MB	34.99 MB	🚨 +581 KB 🚨
Bundle Size Analyzer	Link	Link