Maintenance: Add assertions outside step incorrectly nested in interactions panel

[majiayu000]

Closes #19401

What I did

Added regression tests for the step/waitFor nesting bug in the interactions panel. When a play function uses await step('name', callback) followed by await waitFor(() => expect(...)), assertions inside waitFor could appear nested under the collapsed step instead of under waitFor.

After investigation, the significant code restructuring (moving instrumenter from addons/interactions to code/core, refactoring the instrumenter) appears to have fixed the underlying bug. The instrumenter now correctly restores the ancestors state after async step callbacks complete, so waitFor calls that follow a step no longer inherit the step's call ID in their ancestors.

These tests serve as regression guards to ensure the fix stays in place:

• instrumenter.test.ts: Two new tests verifying that calls inside waitFor after a step have correct ancestors (only waitFor ID, not step ID), including retry scenarios.
• Panel.test.ts: New test verifying that collapsing a step in the interactions panel does not hide subsequent waitFor calls and their children.

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 required — this PR only adds regression tests. The tests verify correct behavior by asserting on the ancestors array of instrumented calls and on the isHidden state of panel rows.

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>

Summary by CodeRabbit

• Tests
  • Added test coverage for interaction hiding behavior when collapsing steps in component testing.
  • Added test coverage for call nesting behavior with the intercept option in the instrumenter.

[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: b80d185d-072d-43f6-bfdc-09e52f4116a2

📥 Commits

Reviewing files that changed from the base of the PR and between 33afce2 and d78e2d5.

📒 Files selected for processing (2)

• code/core/src/component-testing/components/Panel.test.ts
• code/core/src/instrumenter/instrumenter.test.ts

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📝 Walkthrough

Walkthrough

Two test cases are added to verify interaction handling behavior: one for collapse interactions hiding only direct child steps, and another for ensuring calls after an interceptable step are not nested within that step's context.

Changes

Cohort / File(s)	Summary
Test Coverage for Interaction Collapse code/core/src/component-testing/components/Panel.test.ts	New test case validates that collapsing a step call hides only its direct child interactions while unrelated waitFor calls and their descendants remain visible.
Test Coverage for Intercept Behavior code/core/src/instrumenter/instrumenter.test.ts	New test case verifies that when using { intercept: true }, calls made after an interceptable step are not nested within that step's execution context, with proper ancestor tracking.

Estimated code review effort

🎯 3 (Moderate) | ⏱️ ~25 minutes

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Package Benchmarks

^{Commit: 81ac5b2, ran on 27 March 2026 at 12:30:46 UTC}

No significant changes detected, all good. 👏