Docs: Deprecate ExternalDocs

[Sidnioulz]

What I did

Deprecated ExternalDocs, as per internal team discussions.

Checklist for Contributors

Manual testing

• Try to render ExternalDocs in a side project
• Notice the deprecation warning
  workflow run --repo storybookjs/storybook publish.yml --field pr=<PR_NUMBER>`_

Summary by CodeRabbit

• Deprecations

  • ExternalDocs and ExternalDocsContainer components are now deprecated and scheduled for removal in Storybook 11.

• Documentation

  • Updated migration guide with new section documenting the transition path for version 10.5.0.

[Copilot]

Pull request overview

This PR deprecates the ExternalDocs and ExternalDocsContainer blocks from @storybook/addon-docs, surfacing runtime deprecation warnings and documenting the change in the migration guide.

Changes:

• Added a new migration entry describing the deprecation and planned removal in Storybook 11.
• Emitted deprecation warnings when ExternalDocs and ExternalDocsContainer are rendered.
• Aligned the MIGRATION table-of-contents entry text for the TanStack Router migration section.

Reviewed changes

Copilot reviewed 3 out of 3 changed files in this pull request and generated no comments.

File	Description
MIGRATION.md	Adds a 10.4.0 → 10.5.0 migration note and TOC entries for the ExternalDocs deprecation.
code/addons/docs/src/blocks/blocks/external/ExternalDocsContainer.tsx	Logs a deprecation warning when ExternalDocsContainer is used.
code/addons/docs/src/blocks/blocks/external/ExternalDocs.tsx	Logs a deprecation warning when ExternalDocs is used.

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[coderabbitai]

No actionable comments were generated in the recent review. 🎉

ℹ️ Recent review info

⚙️ Run configuration

Configuration used: Organization UI

Review profile: CHILL

Plan: Pro

Run ID: feca2227-54e3-475f-8ada-566a89a2b849

📥 Commits

Reviewing files that changed from the base of the PR and between 10386ac and 1195a1e.

📒 Files selected for processing (3)

• MIGRATION.md
• code/addons/docs/src/blocks/blocks/external/ExternalDocs.tsx
• code/addons/docs/src/blocks/blocks/external/ExternalDocsContainer.tsx

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📝 Walkthrough

Walkthrough

This PR deprecates ExternalDocs and ExternalDocsContainer components from the docs addon. Both components now emit runtime deprecation warnings via the deprecate utility. Migration documentation is added to guide users toward alternatives before removal in Storybook 11.

Changes

ExternalDocs and ExternalDocsContainer Deprecation

Layer / File(s)	Summary
Runtime deprecation warnings in components code/addons/docs/src/blocks/blocks/external/ExternalDocs.tsx, code/addons/docs/src/blocks/blocks/external/ExternalDocsContainer.tsx	ExternalDocs and ExternalDocsContainer import deprecate from the internal client logger and call it within their component bodies to emit deprecation notices indicating removal in Storybook 11.
Migration documentation MIGRATION.md	The table of contents is updated with a new "10.4.0 to 10.5.0" section entry, and a new subsection explains that both components are deprecated, will be removed in Storybook 11, and requests users to open issues describing their use cases.

Estimated code review effort

🎯 1 (Trivial) | ⏱️ ~5 minutes

✨ Finishing Touches

📝 Generate docstrings

• Create stacked PR
• Commit on current branch

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