Agents: Document that next is the base branch

[kasperpeulen]

Closes #

What I did

Added a "Base branch" entry to the Repository Overview section in AGENTS.md, documenting that next is the base branch and all PRs should target it instead of main.

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

No manual testing necessary — this is a documentation-only change to AGENTS.md.

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

• 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

This PR does not have a canary release associated. You can request a canary release of this pull request by mentioning the @storybookjs/core team here.

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

[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: a65ffc46-6ca4-46ad-b0dd-a82fc2f469db

📥 Commits

Reviewing files that changed from the base of the PR and between a571619 and 0d30f65.

📒 Files selected for processing (1)

• AGENTS.md

---

📝 Walkthrough

Walkthrough

Documentation update to AGENTS.md clarifying that the base branch should be "next" rather than "main" for repository contributions. No functional code changes.

Changes

Cohort / File(s)	Summary
Documentation AGENTS.md	Added clarification specifying base branch should target "next" instead of "main".

Estimated code review effort

🎯 1 (Trivial) | ⏱️ ~1 minute

📝 Coding Plan

• Generate coding plan for human review comments

---

_{Comment @coderabbitai help to get the list of available commands and usage tips.}